Quick Revision
This section deals with quick revision capsules and chapter-wise important points — a ready reckoner for all subjects, organised Unit-wise and Topic-wise.
1BIOLOGY- Botany
VIRUS
VIRUS
IMPORTANT POINTS TO REMEMBER
• Virus Properties:
• Viruses can be defined as ultramicroscopic, filterable, infectious, obligate parasitic entities which are composed of nucleoproteins and multiply in the living host only (obligate intracellular parasites).
• Probably there are no cells in nature that escape infection by one or more kinds of viruses. (Viruses that infect bacteria are called bacteriophages.)
• Outside the cell, they consist of particles called virions.
• Virions range in size from as small as the poliovirus shown above magnified some 450,000 times (courtesy of A. R. Taylor), which is 30 nm in diameter (about the size of a ribosome) to as large as the vaccinia virus which, at 230 nm, is larger than some bacteria.
• Virus Discoveries:
o In 1892, Iwanowiski gave first scientific proof for the existence of viruses.
o Beijerinck first of all named the infectious fluid as "Contagium Vivum Fluidum" and subsequently called it as Virus. So he is considered as father of Virology.
o Tobacco Mosaic Virus (TMV) was the first that was studied under Electron Microscope by Takahashi and Rawlins in 1933.
o W.M.Stanley (1935) first of all isolated T.M.V. in crystalline form.
o Twort (1915) discovered a virus infecting bacterium Escherichia coli and it was named as Bacteriophage by d’Herelle in 1917.
o Viruses are of different shapes e.g. Rod-Shaped (TMV), spherical (Poliomyelitis), Tadpole like (Bacteriophage).
o Bawden (1936) and Darlington (1944) suggested that all viruses consist of a protein coat called ‘Capsid’ over ‘a nucleic acid core’ (RNA or DNA).
Virus Size: Less than 200 mµ.
• Smallest virus is foot and mouth disease virus (10 mµ).
• Largest virus is smallpox virus or virus-Variola (250 mµ).
•
Virus Shape:
• Rod shaped - TMV.
• Tadpole-like - Bacteriophages.
• Variable, e.g.. Brick shaped - Smallpox virus.
• Spherical - Influenza virus.
Symmetry of viruses
• Helical symmetry: Capsomeres are arranged in helical manner in the capsid, e.g., TMV and influenza virus.
• Cubical symmetry: Capsomeres are arranged on the surface to form a 20 sided cube, e.g.. Turnip Mosaic Virus.
• Bisymmetrical or Mixed symmetry: e.g., Bacterio¬phages,
• The virion consists of
o An outer shell, the capsid, made of protein. The capsid is responsible for
protecting the contents of the core
establishing what kind of cell the virion can attach to
infecting that cell
Some viruses contain other ingredients (e.g., lipids, carbohydrates), but these are derived from their host cells.
o an interior core containing
the genome; either DNA or RNA The genes are few in number (3 - 100 depending on the species). They encode those proteins needed for viral reproduction that the host cell will not supply.
Often, one or more proteins (enzymes) needed to start the process of reproduction within the host cell
Virus: Life Cycle
• The virion attaches to the surface of the host cell (usually binding to a specific cell surface molecule that accounts for the specificity of the infection). Example: HIV-1, the cause of AIDS, binds to the chemokine receptor CCR5 found on human lymphocytes and macrophages.
• Once inside the cell, the virions are uncoated.
• Viral genes begin to expressed leading to the synthesis of proteins needed for
o replication of the genome
o synthesis of new proteins to make new capsids and cores.
• The details of these processes differ for different types of viruses and are described below for each type.
• Chemical composition: Chemically there are two components of viruses: (1) Nucleic acid core Either RNA or DNA; (2) Protein coat.
Viral Genomes
• Either DNA or RNA, never both.
• Generally in plant viruses, RNA is present but in Cauliflower mosaic virus, DNA is present.
• Generally in animal viruses, DNA is present but in following animal viruses, RNA is present:
(i) Influenza virus: Single stranded RNA.
(ii) Rous sarcoma virus: Single stranded RNA.
(iii) AIDS virus: Single stranded RNA.
• Retroviruses: Single stranded RNA viruses (e.g. AIDS virus) which carry few molecules of reverse transcriptase enzyme (which copies RNA into DNA, i.e., reverse transcription), are called retroviruses.
(iv) Poliomyelitis virus: Single stranded RNA.
(v) Reovirus: Double stranded RNA.
• In bacteriophages, generally DNA is present but in MS2, F2, r-17 bacteriophages, RNA is present.
• Usually DNA is double stranded but in φ×174 Bacteriophage and S/3. E. coli phage, DNA is single stranded.
• Usually RNA is single stranded but in Reoviruses, Wound tumour viruses and Rice dwarf virus, RNA is double stranded.
• (Total number of genes is about a hundred for a large virus, e.g., Vaccinia (cowpox virus) or 3 or 4 for the smallest virus).
• Protein coat: It is known as capsid and it is made of structural units called capsomeres. Number, size and structure of capsomeres vary and these capsomeres are arranged in different manners to form different types of symmetry. (As in a virus particle, protein shell or coat (capsid) surrounds the genome (nucleic acid) and thus is called nucleocapsid).
• In some mammalian viruses, outside the capsid there is another membrane which is known as limiting membrane or mantle.
DNA viruses can be further divided into
• those that have their genes on a double-stranded DNA molecule (dsDNA). Example: smallpox
• those that have their genes on a molecule of single-stranded DNA (ssDNA). Example: Adeno-Associated Virus (AAV).
RNA viruses occur in four distinct groups:
1. Those with a genome that consists of single-stranded antisense RNA; that is, RNA that is the complement of the message sense. This is also called negative-stranded RNA. Examples: measles, Ebola
2. Those with a genome that consists of single-stranded sense RNA; that is, the RNA has message sense (can act as a messenger RNA - mRNA). This is also called positive-stranded RNA. Examples: poliovirus
3. Those with a genome made of several pieces of double-stranded RNA. Example: reovirus.
4. Retroviruses. Their RNA (also single-stranded) is copied by reverse transcriptase into a DNA genome within the host cell. Example: HIV-1
DNA Viruses
1. Genome is a molecule of double-stranded DNA
Examples:
• smallpox (variola)
• vaccinia (used to immunize against smallpox until the disease was eliminated from the planet)
• varicella-zoster (causes chicken pox the first time; shingles the second)
• herpesviruses
o herpes simplex viruses
HSV-1 — usually infects the trigeminal nerves periodically causing "cold sores" on the lips and face
HSV-2 — usually infects the genitals
o KSHV; causes Kaposi's sarcoma in AIDS patients and other people with suppressed immune systems. Also called human herpesvirus 8 (HHV-8).
o cytomegalovirus (CMV); most of us have it; can cause blindness — even death — in people with suppressed immune systems. Binds to the epidermal growth factor receptor (EGFR) on the cells.
o Epstein-Barr virus (EBV); causes mononucleosis and has been implicated in the development of Burkitt's lymphoma (a cancer) and Hodgkin's disease. Its genome has been completely sequenced: 172,282 base pairs of DNA encoding 80 genes.
• adenoviruses
• How herpesviruses (HSV, CMV, and EBV) and adenoviruses evade the immune responses of their host.
• SV40; a virus that infects primate cells and causes tumors in rodent cells.
• Some bacteriophages
o T2 and T4; from which much early information about gene structure and expression was learned. [Links]
o lambda; a popular vector [example]
The essential elements of the infective cycle of DNA bacteriophages consist of:
• The virions attach to the surface of their host cell (a).
• The proteins of the capsid inject the DNA core into the cell (b).
• Once within the cell, some of the bacteriophage genes (the "early" genes) are transcribed (by the host's RNA polymerase) and translated (by the host's ribosomes, tRNA, etc.) to produce enzymes that will make many copies of the phage DNA and will turn off (even destroy) the host's DNA.
• As fresh copies of phage DNA accumulate, other genes (the "late" genes) are transcribed and translated to form the proteins of the capsid (c).
• The stockpile of DNA cores and capsid proteins are assembled into complete virions (d).
• Another "late" gene is transcribed and translated into molecules of lysozyme. The lysozyme attacks the peptidoglycan wall (from the inside, of course).
• Eventually the cell ruptures and releases its content of virions ready to spread the infection to new host cells (e).
Hepatitis B
The genome of hepatitis B ("serum hepatitis") is also dsDNA, but its mode of replication is different from the other dsDNA viruses.
• Once inside its host cell (a liver cell), the virion core enters the nucleus.
• The viral DNA is transcribed (by the host's RNAP II) into molecules of mRNA.
• These enter the cytoplasm where they are translated (again by host ribosomes, etc.) into the various proteins of the virus, including a viral reverse transcriptase.
• These components are assembled into new viral cores, and in each
• one molecule of mRNA is reverse transcribed into a single strand of DNA, which then serves as the template for the synthesis of the second strand.
2. Genome is single-stranded DNA
Examples:
• phiX-174, another famous bacteriophage (infects E. coli) that helped usher in the modern era of molecular genetics. Its single strand of DNA has 5,386 nucleotides and encodes 10 genes.
• Adeno-associated virus (AAV). This virus, which can only grow in cells infected with adenovirus, shows great promise as a safe and effective vector for introducing therapeutic genes into human patients.
RNA Viruses
1. Negative-stranded RNA viruses: genome consists of one or more molecules of single-stranded "antisense" RNA
Examples:
• measles
• mumps
• respiratory syncytial virus (RSV), parainfluenza viruses (PIV), and human metapneumovirus. (In the U.S., these close relatives account for hundreds of thousands of hospital visits each year, mostly by children.)
• rabies
• Ebola
• influenza
Method of replication
• In addition to its antisense RNA genome, the core of the virion contains an RNA replicase, which is an RNA-dependent RNA polymerase.
• Once released in the host cell, this polymerase makes many complementary copies of the genome, which are "sense" and serve as messenger RNAs.
• These are translated into the proteins needed to assemble fresh virions, e.g., capsid proteins and RNA polymerase.
Note that this strategy
• provides many copies of mRNA
• depends on the virion having its own RNA replicase (because the host cell does not) (So, naked RNA molecules of these viruses are not infectious - in contrast to the next group: the positive-stranded RNA viruses)
2. Positive-stranded RNA: genome is a molecule of single-stranded "sense" RNA
Examples:
• polioviruses ("picornaviruses")
• rhinoviruses (frequent cause of the common "cold")
• coronaviruses (another frequent cause of the common cold and the chief suspect in the recent (2003) worldwide outbreak of Severe Acute Respiratory Syndrome (SARS)
• rubella ("German" measles)
• yellow fever (a "togavirus")
• West Nile virus (a "flavivirus")
• dengue
• equine encephalitis
• hepatitis A ("infectious hepatitis") and hepatitis C (HCV)
• tobacco mosaic virus (TMV)
Method of replication
• The "sense" RNA encodes an RNA replicase (an RNA-dependent RNA polymerase) that
• is translated by the host machinery (ribosomes, etc.) into the enzyme, which
• catalyzes the synthesis of large numbers of "antisense" replicative intermediates.
• These serve as templates for the synthesis of large numbers of mRNA molecules that
o are translated by the host cell machinery into the proteins needed to make fresh virions
o are incorporated into the new virions.
3. Genome consists of several molecules of double-stranded RNA
Examples:
• reovirus
• several plant viruses
Method of replication
The virus particle contains enzymatic machinery that transcribes each of the dsRNA molecules into a mRNA (complete with cap) and exports these into the cytosol of the infected cell.
4. Retroviruses
These viruses contain a reverse transcriptase that copies their RNA genome into DNA.
Examples:
• The Rous sarcoma virus (RSV)
• HIV-1 and HIV-2, that cause AIDS
• HTLV-1 and HTLV-2; about 3% of the people infected with HTLV-1 develop leukemia.
Latent Viruses
Most of the infective cycles described for the various viruses end in the death of the host cell. Bacterial cells literally burst, a process called lysis, and similar infective cycles are called lytic cycles.
Lysogeny
In some cases, though, the events of the lytic cycle are not completed. E. coli infected by a DNA bacteriophage may resume its normal existence, including reproducing itself.
Where has the virus gone?
It is still there and, in fact, is present in the descendants of the bacterium. That these cells still harbor the virus can be demonstrated by irradiating the cells with ultraviolet rays or treating them with certain chemicals. Such treatment restores the normal lytic cycle. The phage is said to have been "rescued" - hardly the case for its host!
The stable relationship between a bacteriophage and its host is called lysogeny. The viral DNA actually becomes replicated when the host's DNA is replicated prior to each cell division. During lysogeny, the phage is called a prophage.
In some cases, the prophage DNA becomes inserted into the chromosome of its host. In fact, when the phage is "rescued", the released virions may contain some host genes as well as their own. When these virions infect new hosts, they insert these bacterial genes into them. This process of genetic transfer, a virus-mediated transformation, is called transduction.
What does the prophage do while it is a part of its host genome? It can express certain of its genes. For example, the gene that encodes diphtheria toxin is the property of a prophage in the diphtheria bacillus, not of the bacillus itself.
Some animal viruses can also establish latent infections. Simian virus 40 (SV40) is a DNA virus that produces
• a lytic infection in the kidney cells of the African green monkey (these cells are used to cultivate viruses in the lab)
• but a latent infection in the cells of humans, mice, rats, and hamsters. Like lysogeny in bacteria, the SV40 genome becomes incorporated in the DNA of its host (in chromosome 7 in human cells).
Although a human cell with harboring SV40 shows no outward sign of the virus, its presence can be detected by:
• the appearance of viral-encoded antigens in the host cell
• the ability of these cells to cause a lytic infection in African green monkey cells when fused with them.
Latent infections may also cause the cell to become cancerous. The cell has become transformed. (In these cases, the word fulfills both of its biological meanings:
• "transformed" by the incorporation of new DNA
• "transformed" as it becomes cancerous.
In humans,
• lytic infections of plasma cells by the Epstein-Barr virus (EBV) occur in mononucleosis;
• latent infections of B cells by EBV predispose the person to lymphoma.
while
• lytic infections by human papilloma virus (HPV) cause genital warts;
• latent infections by some strains of HPV lead to cervical cancer.
TMV (Tobacco Mosaic Virus)
• It is the most thoroughly studied virus and was discovered by the Russian worker D. Ivanowski ( 1892).
• It is rod shaped virus measuring 300 x 18 nm.
• It is having helical symmetry.
• Having single stranded RNA which is 330 nm in length and having 7300 nucleotides.
• Number of capsomeres in capsid is 2130.
• 5% RNA and 95% protein is present in TMV.
Influenza virus
• Spherical virus, infecting respiratory tract.
• Having helical symmetry. 10% RNA and 90% protein is present in influenza virus.
• Having single stranded RNA, killed at 65°C and active at low temperature.
• Cryptogram of influenza virus: R/I: 2-3/10: S/E: V/A
• Viruses contain only one kind of nucleic acid (DNA or RNA).
• Viruses which contain ss-DNA are called ‘Gemini viruses’. φ×174 phages are geminiviruses. They were reported by Sinsheimer.
• Single stranded DNA is found in φ×174 and S13 phages of Escherichia coli and double stranded RNA is found in Reovirus and wound tumour virus.
• Viruses containing double stranded DNA (ds-DNA) are called caulimo viruses e.g. Cauliflower Mosaic Virus (CaMV), Dahlia Mosaic Virus (DMV) etc.
• Viruses containing single-stranded DNA are called geminiviruses.
• Viruses attacking bacteria are called bacteriophages.
• Viruses that attack blue green algae/cyanobacteria and cause diseases are called cyanophages.
• Tobacco mosaic virus (TMV) is hollow, rod–like virus containing single stranded RNA surrounded by 2200 protein sub-units called capsomeres.
• Viruses usually lack enzymes. The first enzyme discovered was neuraminidase in influenia-virus and Paramyxoviruses. DNA and RNA Polymerases found in viruses have been collectively termed as transcriptases which synthesize m-RNA from virion nucleic acid. A reverse transcriptase has been isolated in pure form from RNA tumor virus which synthesizes DNA from single stranded RNA template.
• The insect which carries a virus disease is called a vector. Aphids transmit more plant viruses than any other insect. The period of development of infectivity for the virus within the vector is called incubation period.
• Satellite tobacco necrosis virus is parasite on another virus.
• Plant viruses contain RNA but bacteriophages, cauliflower mosaic virus and cyanophages have DNA.
• Cyanophage viruses infect blue-green algae. Safferman and Morris (1963) discovered the cyanophage virus infection Lyngbya, Phormidium and Plectonema, and named it LPP-1, by taking the initial letter of these algal hosts.
• In India, Prof. R.N. Singh discovered a few cyanophage viruses such as C-1 (infectiong Cylind ropermum) and AR-1 (infection Anabaenopsis and Raphidiopsis).
• Mycoplasma, also called pleuro-pneumonia-like organisms (PPLO) have smallest cells (0.1-1µm), having a cell membrane but lack cell wall. They contain both DNA and RNA. DNA is in the form of two stranded filament while RNA is found in the form of granules combined with protein, resembling ribosomes of larger cells. They cause various diseases in animals and plants. Little leaf disease of brinjal, found in citrus greening, sandal spike, grassy shoot of sugarcane etc. Due to pleiomorphism they are called jockers in microbiological pack.
• The sub-viral entities devoid of their own genetic material (DNA or RNA) are called 'prions' or 'infectious proteins'.
• Prions (pronounced pree-ahns) are agents that cause a novel type of fatal brain disease. Bovine spongiform encephalopathy (BSE or mad cow disease), sheep scrapie and Creutzfeldt-Jakob disease (CJD) of humans are examples of prion diseases. Prions enter cells and convert normal proteins found within the cells into prions just like themselves. The normal cell proteins have all the same "parts" as the prions--specifically the same amino acid building blocks--but they fold differently.
• The infectious nucleic acid (RNA) without protein coat is called viroid. Viroids are also called ‘naked viruses’ or ‘metaviruses’. Viroids are smallest infectious agents. The first viroid, discovered by T.O. Diener (1971) was Potato Spindle Tuber Viroid (PSTV) which causes potato spindle tuber disease. Some other important diseases caused by viroids are Citrus exocortis disease, Chrysanthemum stunt disease, Tomato Bunchy Top disease.
• Acquired Immuno Deficiency Syndrome (AIDS) is an infectious disease caused by a retrovirus Human T-Lymphotrophic Virus type III (HTLV III). This virus has a single stranded RNA. However. an International Committee of workers has proposed a name, ‘Human Immunodeficiency Virus (HIV)’ for this virus.
• Human Diseases: Polio, Pox, Measles, Mumps, Hydrophobia, Influenza, Cancer; Conjunctivitis, En¬ cephalitis, etc.
• Plant diseases: Tobcco Mosaic, Cucumber Mosaic, Cauliflower Mosaic, Satellite Tobacco Necrosis, Tomato Mosaic, etc.
• Viruses transmitted by insects are called Arboviruses. Viruses causing Dengue, encephalitis etc are arboviruses.
• Viruses which enter inside host cell as intact structures are called Adenoviruses. Well defined protein coat is absent in Adenoviruses.
• Protein coat of the virus is termed as capsid; units of capsid are capsomeres. A virus drops its infective part i.e., nucleic acid alone inside host cell; empty protein coat remains outside. This empty protein coat, which remains outside the host called ghost protein, disappears later on. Raw material for new protein coat of the progeny viruses is contributed by the host.
• Subviral agent having infectious nucleic acid alone is called viroid. Viroid lacks protein coat. Spindle disease in potato tuber is caused by viroid, which is PSTV. Viroids were discovered by Diener and Rayner.
• Viroids contain only very low mol. wt. RNA and no protein coat.
• Viroids cause Potato spindle tuber viroid disease (PSTV), Chrysanthemum stunt, Citrus exocortis, Cucumber pale fruit, etc.
• Stanley B. Prusiner discovered certain infectious agents or slow viruses which contain only proteins. Prions cause scrapie disease in sheep and goat and Kuru disease (disease of nervous system). Prusiner got Nobel Prize for this work in 1997.
• Viral vaccines: The purpose of viral vaccine is to utilize the immune response of the host to prevent viral diseases. Vaccination is the most cost effective method of prevention of serious viral infection.
• Potato spindle tuber disease is caused by viroid.
• Watery stipe disease of mushroom is caused by virus.
IMPORTANT POINTS TO REMEMBER
• Virus Properties:
• Viruses can be defined as ultramicroscopic, filterable, infectious, obligate parasitic entities which are composed of nucleoproteins and multiply in the living host only (obligate intracellular parasites).
• Probably there are no cells in nature that escape infection by one or more kinds of viruses. (Viruses that infect bacteria are called bacteriophages.)
• Outside the cell, they consist of particles called virions.
• Virions range in size from as small as the poliovirus shown above magnified some 450,000 times (courtesy of A. R. Taylor), which is 30 nm in diameter (about the size of a ribosome) to as large as the vaccinia virus which, at 230 nm, is larger than some bacteria.
• Virus Discoveries:
o In 1892, Iwanowiski gave first scientific proof for the existence of viruses.
o Beijerinck first of all named the infectious fluid as "Contagium Vivum Fluidum" and subsequently called it as Virus. So he is considered as father of Virology.
o Tobacco Mosaic Virus (TMV) was the first that was studied under Electron Microscope by Takahashi and Rawlins in 1933.
o W.M.Stanley (1935) first of all isolated T.M.V. in crystalline form.
o Twort (1915) discovered a virus infecting bacterium Escherichia coli and it was named as Bacteriophage by d’Herelle in 1917.
o Viruses are of different shapes e.g. Rod-Shaped (TMV), spherical (Poliomyelitis), Tadpole like (Bacteriophage).
o Bawden (1936) and Darlington (1944) suggested that all viruses consist of a protein coat called ‘Capsid’ over ‘a nucleic acid core’ (RNA or DNA).
Virus Size: Less than 200 mµ.
• Smallest virus is foot and mouth disease virus (10 mµ).
• Largest virus is smallpox virus or virus-Variola (250 mµ).
•
Virus Shape:
• Rod shaped - TMV.
• Tadpole-like - Bacteriophages.
• Variable, e.g.. Brick shaped - Smallpox virus.
• Spherical - Influenza virus.
Symmetry of viruses
• Helical symmetry: Capsomeres are arranged in helical manner in the capsid, e.g., TMV and influenza virus.
• Cubical symmetry: Capsomeres are arranged on the surface to form a 20 sided cube, e.g.. Turnip Mosaic Virus.
• Bisymmetrical or Mixed symmetry: e.g., Bacterio¬phages,
• The virion consists of
o An outer shell, the capsid, made of protein. The capsid is responsible for
protecting the contents of the core
establishing what kind of cell the virion can attach to
infecting that cell
Some viruses contain other ingredients (e.g., lipids, carbohydrates), but these are derived from their host cells.
o an interior core containing
the genome; either DNA or RNA The genes are few in number (3 - 100 depending on the species). They encode those proteins needed for viral reproduction that the host cell will not supply.
Often, one or more proteins (enzymes) needed to start the process of reproduction within the host cell
Virus: Life Cycle
• The virion attaches to the surface of the host cell (usually binding to a specific cell surface molecule that accounts for the specificity of the infection). Example: HIV-1, the cause of AIDS, binds to the chemokine receptor CCR5 found on human lymphocytes and macrophages.
• Once inside the cell, the virions are uncoated.
• Viral genes begin to expressed leading to the synthesis of proteins needed for
o replication of the genome
o synthesis of new proteins to make new capsids and cores.
• The details of these processes differ for different types of viruses and are described below for each type.
• Chemical composition: Chemically there are two components of viruses: (1) Nucleic acid core Either RNA or DNA; (2) Protein coat.
Viral Genomes
• Either DNA or RNA, never both.
• Generally in plant viruses, RNA is present but in Cauliflower mosaic virus, DNA is present.
• Generally in animal viruses, DNA is present but in following animal viruses, RNA is present:
(i) Influenza virus: Single stranded RNA.
(ii) Rous sarcoma virus: Single stranded RNA.
(iii) AIDS virus: Single stranded RNA.
• Retroviruses: Single stranded RNA viruses (e.g. AIDS virus) which carry few molecules of reverse transcriptase enzyme (which copies RNA into DNA, i.e., reverse transcription), are called retroviruses.
(iv) Poliomyelitis virus: Single stranded RNA.
(v) Reovirus: Double stranded RNA.
• In bacteriophages, generally DNA is present but in MS2, F2, r-17 bacteriophages, RNA is present.
• Usually DNA is double stranded but in φ×174 Bacteriophage and S/3. E. coli phage, DNA is single stranded.
• Usually RNA is single stranded but in Reoviruses, Wound tumour viruses and Rice dwarf virus, RNA is double stranded.
• (Total number of genes is about a hundred for a large virus, e.g., Vaccinia (cowpox virus) or 3 or 4 for the smallest virus).
• Protein coat: It is known as capsid and it is made of structural units called capsomeres. Number, size and structure of capsomeres vary and these capsomeres are arranged in different manners to form different types of symmetry. (As in a virus particle, protein shell or coat (capsid) surrounds the genome (nucleic acid) and thus is called nucleocapsid).
• In some mammalian viruses, outside the capsid there is another membrane which is known as limiting membrane or mantle.
DNA viruses can be further divided into
• those that have their genes on a double-stranded DNA molecule (dsDNA). Example: smallpox
• those that have their genes on a molecule of single-stranded DNA (ssDNA). Example: Adeno-Associated Virus (AAV).
RNA viruses occur in four distinct groups:
1. Those with a genome that consists of single-stranded antisense RNA; that is, RNA that is the complement of the message sense. This is also called negative-stranded RNA. Examples: measles, Ebola
2. Those with a genome that consists of single-stranded sense RNA; that is, the RNA has message sense (can act as a messenger RNA - mRNA). This is also called positive-stranded RNA. Examples: poliovirus
3. Those with a genome made of several pieces of double-stranded RNA. Example: reovirus.
4. Retroviruses. Their RNA (also single-stranded) is copied by reverse transcriptase into a DNA genome within the host cell. Example: HIV-1
DNA Viruses
1. Genome is a molecule of double-stranded DNA
Examples:
• smallpox (variola)
• vaccinia (used to immunize against smallpox until the disease was eliminated from the planet)
• varicella-zoster (causes chicken pox the first time; shingles the second)
• herpesviruses
o herpes simplex viruses
HSV-1 — usually infects the trigeminal nerves periodically causing "cold sores" on the lips and face
HSV-2 — usually infects the genitals
o KSHV; causes Kaposi's sarcoma in AIDS patients and other people with suppressed immune systems. Also called human herpesvirus 8 (HHV-8).
o cytomegalovirus (CMV); most of us have it; can cause blindness — even death — in people with suppressed immune systems. Binds to the epidermal growth factor receptor (EGFR) on the cells.
o Epstein-Barr virus (EBV); causes mononucleosis and has been implicated in the development of Burkitt's lymphoma (a cancer) and Hodgkin's disease. Its genome has been completely sequenced: 172,282 base pairs of DNA encoding 80 genes.
• adenoviruses
• How herpesviruses (HSV, CMV, and EBV) and adenoviruses evade the immune responses of their host.
• SV40; a virus that infects primate cells and causes tumors in rodent cells.
• Some bacteriophages
o T2 and T4; from which much early information about gene structure and expression was learned. [Links]
o lambda; a popular vector [example]
The essential elements of the infective cycle of DNA bacteriophages consist of:
• The virions attach to the surface of their host cell (a).
• The proteins of the capsid inject the DNA core into the cell (b).
• Once within the cell, some of the bacteriophage genes (the "early" genes) are transcribed (by the host's RNA polymerase) and translated (by the host's ribosomes, tRNA, etc.) to produce enzymes that will make many copies of the phage DNA and will turn off (even destroy) the host's DNA.
• As fresh copies of phage DNA accumulate, other genes (the "late" genes) are transcribed and translated to form the proteins of the capsid (c).
• The stockpile of DNA cores and capsid proteins are assembled into complete virions (d).
• Another "late" gene is transcribed and translated into molecules of lysozyme. The lysozyme attacks the peptidoglycan wall (from the inside, of course).
• Eventually the cell ruptures and releases its content of virions ready to spread the infection to new host cells (e).
Hepatitis B
The genome of hepatitis B ("serum hepatitis") is also dsDNA, but its mode of replication is different from the other dsDNA viruses.
• Once inside its host cell (a liver cell), the virion core enters the nucleus.
• The viral DNA is transcribed (by the host's RNAP II) into molecules of mRNA.
• These enter the cytoplasm where they are translated (again by host ribosomes, etc.) into the various proteins of the virus, including a viral reverse transcriptase.
• These components are assembled into new viral cores, and in each
• one molecule of mRNA is reverse transcribed into a single strand of DNA, which then serves as the template for the synthesis of the second strand.
2. Genome is single-stranded DNA
Examples:
• phiX-174, another famous bacteriophage (infects E. coli) that helped usher in the modern era of molecular genetics. Its single strand of DNA has 5,386 nucleotides and encodes 10 genes.
• Adeno-associated virus (AAV). This virus, which can only grow in cells infected with adenovirus, shows great promise as a safe and effective vector for introducing therapeutic genes into human patients.
RNA Viruses
1. Negative-stranded RNA viruses: genome consists of one or more molecules of single-stranded "antisense" RNA
Examples:
• measles
• mumps
• respiratory syncytial virus (RSV), parainfluenza viruses (PIV), and human metapneumovirus. (In the U.S., these close relatives account for hundreds of thousands of hospital visits each year, mostly by children.)
• rabies
• Ebola
• influenza
Method of replication
• In addition to its antisense RNA genome, the core of the virion contains an RNA replicase, which is an RNA-dependent RNA polymerase.
• Once released in the host cell, this polymerase makes many complementary copies of the genome, which are "sense" and serve as messenger RNAs.
• These are translated into the proteins needed to assemble fresh virions, e.g., capsid proteins and RNA polymerase.
Note that this strategy
• provides many copies of mRNA
• depends on the virion having its own RNA replicase (because the host cell does not) (So, naked RNA molecules of these viruses are not infectious - in contrast to the next group: the positive-stranded RNA viruses)
2. Positive-stranded RNA: genome is a molecule of single-stranded "sense" RNA
Examples:
• polioviruses ("picornaviruses")
• rhinoviruses (frequent cause of the common "cold")
• coronaviruses (another frequent cause of the common cold and the chief suspect in the recent (2003) worldwide outbreak of Severe Acute Respiratory Syndrome (SARS)
• rubella ("German" measles)
• yellow fever (a "togavirus")
• West Nile virus (a "flavivirus")
• dengue
• equine encephalitis
• hepatitis A ("infectious hepatitis") and hepatitis C (HCV)
• tobacco mosaic virus (TMV)
Method of replication
• The "sense" RNA encodes an RNA replicase (an RNA-dependent RNA polymerase) that
• is translated by the host machinery (ribosomes, etc.) into the enzyme, which
• catalyzes the synthesis of large numbers of "antisense" replicative intermediates.
• These serve as templates for the synthesis of large numbers of mRNA molecules that
o are translated by the host cell machinery into the proteins needed to make fresh virions
o are incorporated into the new virions.
3. Genome consists of several molecules of double-stranded RNA
Examples:
• reovirus
• several plant viruses
Method of replication
The virus particle contains enzymatic machinery that transcribes each of the dsRNA molecules into a mRNA (complete with cap) and exports these into the cytosol of the infected cell.
4. Retroviruses
These viruses contain a reverse transcriptase that copies their RNA genome into DNA.
Examples:
• The Rous sarcoma virus (RSV)
• HIV-1 and HIV-2, that cause AIDS
• HTLV-1 and HTLV-2; about 3% of the people infected with HTLV-1 develop leukemia.
Latent Viruses
Most of the infective cycles described for the various viruses end in the death of the host cell. Bacterial cells literally burst, a process called lysis, and similar infective cycles are called lytic cycles.
Lysogeny
In some cases, though, the events of the lytic cycle are not completed. E. coli infected by a DNA bacteriophage may resume its normal existence, including reproducing itself.
Where has the virus gone?
It is still there and, in fact, is present in the descendants of the bacterium. That these cells still harbor the virus can be demonstrated by irradiating the cells with ultraviolet rays or treating them with certain chemicals. Such treatment restores the normal lytic cycle. The phage is said to have been "rescued" - hardly the case for its host!
The stable relationship between a bacteriophage and its host is called lysogeny. The viral DNA actually becomes replicated when the host's DNA is replicated prior to each cell division. During lysogeny, the phage is called a prophage.
In some cases, the prophage DNA becomes inserted into the chromosome of its host. In fact, when the phage is "rescued", the released virions may contain some host genes as well as their own. When these virions infect new hosts, they insert these bacterial genes into them. This process of genetic transfer, a virus-mediated transformation, is called transduction.
What does the prophage do while it is a part of its host genome? It can express certain of its genes. For example, the gene that encodes diphtheria toxin is the property of a prophage in the diphtheria bacillus, not of the bacillus itself.
Some animal viruses can also establish latent infections. Simian virus 40 (SV40) is a DNA virus that produces
• a lytic infection in the kidney cells of the African green monkey (these cells are used to cultivate viruses in the lab)
• but a latent infection in the cells of humans, mice, rats, and hamsters. Like lysogeny in bacteria, the SV40 genome becomes incorporated in the DNA of its host (in chromosome 7 in human cells).
Although a human cell with harboring SV40 shows no outward sign of the virus, its presence can be detected by:
• the appearance of viral-encoded antigens in the host cell
• the ability of these cells to cause a lytic infection in African green monkey cells when fused with them.
Latent infections may also cause the cell to become cancerous. The cell has become transformed. (In these cases, the word fulfills both of its biological meanings:
• "transformed" by the incorporation of new DNA
• "transformed" as it becomes cancerous.
In humans,
• lytic infections of plasma cells by the Epstein-Barr virus (EBV) occur in mononucleosis;
• latent infections of B cells by EBV predispose the person to lymphoma.
while
• lytic infections by human papilloma virus (HPV) cause genital warts;
• latent infections by some strains of HPV lead to cervical cancer.
TMV (Tobacco Mosaic Virus)
• It is the most thoroughly studied virus and was discovered by the Russian worker D. Ivanowski ( 1892).
• It is rod shaped virus measuring 300 x 18 nm.
• It is having helical symmetry.
• Having single stranded RNA which is 330 nm in length and having 7300 nucleotides.
• Number of capsomeres in capsid is 2130.
• 5% RNA and 95% protein is present in TMV.
Influenza virus
• Spherical virus, infecting respiratory tract.
• Having helical symmetry. 10% RNA and 90% protein is present in influenza virus.
• Having single stranded RNA, killed at 65°C and active at low temperature.
• Cryptogram of influenza virus: R/I: 2-3/10: S/E: V/A
• Viruses contain only one kind of nucleic acid (DNA or RNA).
• Viruses which contain ss-DNA are called ‘Gemini viruses’. φ×174 phages are geminiviruses. They were reported by Sinsheimer.
• Single stranded DNA is found in φ×174 and S13 phages of Escherichia coli and double stranded RNA is found in Reovirus and wound tumour virus.
• Viruses containing double stranded DNA (ds-DNA) are called caulimo viruses e.g. Cauliflower Mosaic Virus (CaMV), Dahlia Mosaic Virus (DMV) etc.
• Viruses containing single-stranded DNA are called geminiviruses.
• Viruses attacking bacteria are called bacteriophages.
• Viruses that attack blue green algae/cyanobacteria and cause diseases are called cyanophages.
• Tobacco mosaic virus (TMV) is hollow, rod–like virus containing single stranded RNA surrounded by 2200 protein sub-units called capsomeres.
• Viruses usually lack enzymes. The first enzyme discovered was neuraminidase in influenia-virus and Paramyxoviruses. DNA and RNA Polymerases found in viruses have been collectively termed as transcriptases which synthesize m-RNA from virion nucleic acid. A reverse transcriptase has been isolated in pure form from RNA tumor virus which synthesizes DNA from single stranded RNA template.
• The insect which carries a virus disease is called a vector. Aphids transmit more plant viruses than any other insect. The period of development of infectivity for the virus within the vector is called incubation period.
• Satellite tobacco necrosis virus is parasite on another virus.
• Plant viruses contain RNA but bacteriophages, cauliflower mosaic virus and cyanophages have DNA.
• Cyanophage viruses infect blue-green algae. Safferman and Morris (1963) discovered the cyanophage virus infection Lyngbya, Phormidium and Plectonema, and named it LPP-1, by taking the initial letter of these algal hosts.
• In India, Prof. R.N. Singh discovered a few cyanophage viruses such as C-1 (infectiong Cylind ropermum) and AR-1 (infection Anabaenopsis and Raphidiopsis).
• Mycoplasma, also called pleuro-pneumonia-like organisms (PPLO) have smallest cells (0.1-1µm), having a cell membrane but lack cell wall. They contain both DNA and RNA. DNA is in the form of two stranded filament while RNA is found in the form of granules combined with protein, resembling ribosomes of larger cells. They cause various diseases in animals and plants. Little leaf disease of brinjal, found in citrus greening, sandal spike, grassy shoot of sugarcane etc. Due to pleiomorphism they are called jockers in microbiological pack.
• The sub-viral entities devoid of their own genetic material (DNA or RNA) are called 'prions' or 'infectious proteins'.
• Prions (pronounced pree-ahns) are agents that cause a novel type of fatal brain disease. Bovine spongiform encephalopathy (BSE or mad cow disease), sheep scrapie and Creutzfeldt-Jakob disease (CJD) of humans are examples of prion diseases. Prions enter cells and convert normal proteins found within the cells into prions just like themselves. The normal cell proteins have all the same "parts" as the prions--specifically the same amino acid building blocks--but they fold differently.
• The infectious nucleic acid (RNA) without protein coat is called viroid. Viroids are also called ‘naked viruses’ or ‘metaviruses’. Viroids are smallest infectious agents. The first viroid, discovered by T.O. Diener (1971) was Potato Spindle Tuber Viroid (PSTV) which causes potato spindle tuber disease. Some other important diseases caused by viroids are Citrus exocortis disease, Chrysanthemum stunt disease, Tomato Bunchy Top disease.
• Acquired Immuno Deficiency Syndrome (AIDS) is an infectious disease caused by a retrovirus Human T-Lymphotrophic Virus type III (HTLV III). This virus has a single stranded RNA. However. an International Committee of workers has proposed a name, ‘Human Immunodeficiency Virus (HIV)’ for this virus.
• Human Diseases: Polio, Pox, Measles, Mumps, Hydrophobia, Influenza, Cancer; Conjunctivitis, En¬ cephalitis, etc.
• Plant diseases: Tobcco Mosaic, Cucumber Mosaic, Cauliflower Mosaic, Satellite Tobacco Necrosis, Tomato Mosaic, etc.
• Viruses transmitted by insects are called Arboviruses. Viruses causing Dengue, encephalitis etc are arboviruses.
• Viruses which enter inside host cell as intact structures are called Adenoviruses. Well defined protein coat is absent in Adenoviruses.
• Protein coat of the virus is termed as capsid; units of capsid are capsomeres. A virus drops its infective part i.e., nucleic acid alone inside host cell; empty protein coat remains outside. This empty protein coat, which remains outside the host called ghost protein, disappears later on. Raw material for new protein coat of the progeny viruses is contributed by the host.
• Subviral agent having infectious nucleic acid alone is called viroid. Viroid lacks protein coat. Spindle disease in potato tuber is caused by viroid, which is PSTV. Viroids were discovered by Diener and Rayner.
• Viroids contain only very low mol. wt. RNA and no protein coat.
• Viroids cause Potato spindle tuber viroid disease (PSTV), Chrysanthemum stunt, Citrus exocortis, Cucumber pale fruit, etc.
• Stanley B. Prusiner discovered certain infectious agents or slow viruses which contain only proteins. Prions cause scrapie disease in sheep and goat and Kuru disease (disease of nervous system). Prusiner got Nobel Prize for this work in 1997.
• Viral vaccines: The purpose of viral vaccine is to utilize the immune response of the host to prevent viral diseases. Vaccination is the most cost effective method of prevention of serious viral infection.
• Potato spindle tuber disease is caused by viroid.
• Watery stipe disease of mushroom is caused by virus.
LICHENS
LICHENS
Lichens growing on Called as
Rocks Saxicolus
Wood Lignicolous
Bark Corticolous
Ground Terricolous
Type of Lichens Example
Crustose lichens Strigula, Graphis, Rhizocarpon
Foliose lichens Physcia, Chaudhuria, Peltigera, Parmelia
Fruiticose lichens Bryonia, Usnea, Cladonia
• Lichen Usnea is known as Old man’s beard
• Peltigera canina – Dog Lichen, is useful against hydrophobia
• The skull lichen – Parmilia saxilitis
• Litimus is obtained from lichen Rocella and Leconora , stain orcein is also obtained
• Majority of lichens have fungal component belonging to ascomycotina and hence called Ascolichens, e.g. Parmilia, physcia, Leconora, Buellia, Cladonia, Usnea, etc.
• Basidiolichens are rare e.g. Cora
Lichens growing on Called as
Rocks Saxicolus
Wood Lignicolous
Bark Corticolous
Ground Terricolous
Type of Lichens Example
Crustose lichens Strigula, Graphis, Rhizocarpon
Foliose lichens Physcia, Chaudhuria, Peltigera, Parmelia
Fruiticose lichens Bryonia, Usnea, Cladonia
• Lichen Usnea is known as Old man’s beard
• Peltigera canina – Dog Lichen, is useful against hydrophobia
• The skull lichen – Parmilia saxilitis
• Litimus is obtained from lichen Rocella and Leconora , stain orcein is also obtained
• Majority of lichens have fungal component belonging to ascomycotina and hence called Ascolichens, e.g. Parmilia, physcia, Leconora, Buellia, Cladonia, Usnea, etc.
• Basidiolichens are rare e.g. Cora
BACTERIA
IMPORTANT POINTS TO REMEMBER
• The bacteriophage contain an enzyme known as lysozyme.
• Tetanus disease is caused by Clostridium tetane
• Bacteriophage that lyse the bacterial cell shortly after the infection are termed as Virulent.
• Cornybacterim is a gram +ve bacterium.
• Beggiatoa is a sulphur bacterium.
• The protein digesting microbe utilized in flax / jute stem (retting0 is Clostridium fesineum.
• Prions are infectious proteins.
• Prions are discovered by Prusiner et al, made up of proteins only, disease – Scrapie disease of sheep, Kuru disease.
• Streptomycin was discovered by Waksman.
• Corn stunt disease – Spiroplasma
• Plant virus was first crystallized by Stanley.
• Cyclohexamide (actdione) was isolated from Streptomyces griseus.
• Food poisoning (Botulism) is caused by infection of a species of – Clostridium
• Food poisoning (Botulism) is caused by Clostridium botulinum
• Disease caused by bacteria – Tuberculosis
• Rickettsias were first escribed by H.T Ricketts in his studies on Rocky Mountain spotted fever and typhus fever. They are about 0.3 µm in diameter and less than 2 µm in length. They are nonmotile and have a definite cell wall, composed of mucopeptides and are surrounded by capsular material just as in bacteria. They contain both RNA and DNA, and are stained readily by Giemsa’s stain. They reproduce by binary fission. They are found typically in arthropods and may cause diseases in man and other animals. They have yet not been cultured except in the cells of a host they infect. They are classified under bacteria.
• Pure cultures of bacteria were fIrst obtained by J. Lister in 1878 by serial dilutions in liquid media and he named the organism Bacterium lactis.
• Archebacteria are the ancient group of bacteria living in extreme environments. Some are anaerobic and produce. methane and are .called methanogens. They are found in marshes and cattle rumen. In cattle rumen they ferment cellulose. In biogas ferment¬ers they produce methane. Some live in strong brjne and are called halophiles. Some are found in hot acidic sulphur springs as aerobes and anaerobes and they are called thermoacidophiles. Their cell wall consists of polysaccharides and proteins {no pep-tidoglycans). Archebacterial cell membrane contains branched chain lipids which make them heat and acid resistant.
• The term ‘antibiotic’ was coined by Selman Waksman in 1942. Antibiotic is a substance produced by a micro-organism that inhibits the growth of other microorganisms or kills them. Some antibiotics are known as broad spectrum antibiotics because of their ability to act on several pathogenic species.
PLANT DISEASES
Disease Pathogen
1. Citrus canker = Xanthomonas citri
2. Common blight of beans = Xanthomonas phaseoli
3. Crown gall = Agrobcicterium tumefaciens
4. Ear rot of wheat = Corynebacterium tritici
5. Fire blight of apple and pear = Erwinia amylovora
6. Red stripe of sugarcane = Xanthomonas mbrilineans
7. Soft rot of carrots & turnips = Erwinia carotovora
8. Wilt disease or brown rot of potato = Pseudomonas solanaceamm
ANIMAL DISEASES
Disease Pathogen
1. Anthrax = Bacillus anthracis (G+)
2. Cholera = Vibrio cholerae (G-)
3. Diphtheria = Corynebacterium diphtheriae
4. Gonorrhoea = Neisseria gonorrhoeae
5. Leprosy = Mycobacterium leprae
6. Plague = Yersinia pestis
7. Pneumonia = Pneumococcus pneumoniae
8. Syphilis = Treponema pallidum
9. Tetanus or lock jaw = Clm'tridium -tetani
10.. Tuberculosis = Mycobacterium tuberculosis
11. Typhoid = Salmonella typhi
• The bacteriophage contain an enzyme known as lysozyme.
• Tetanus disease is caused by Clostridium tetane
• Bacteriophage that lyse the bacterial cell shortly after the infection are termed as Virulent.
• Cornybacterim is a gram +ve bacterium.
• Beggiatoa is a sulphur bacterium.
• The protein digesting microbe utilized in flax / jute stem (retting0 is Clostridium fesineum.
• Prions are infectious proteins.
• Prions are discovered by Prusiner et al, made up of proteins only, disease – Scrapie disease of sheep, Kuru disease.
• Streptomycin was discovered by Waksman.
• Corn stunt disease – Spiroplasma
• Plant virus was first crystallized by Stanley.
• Cyclohexamide (actdione) was isolated from Streptomyces griseus.
• Food poisoning (Botulism) is caused by infection of a species of – Clostridium
• Food poisoning (Botulism) is caused by Clostridium botulinum
• Disease caused by bacteria – Tuberculosis
• Rickettsias were first escribed by H.T Ricketts in his studies on Rocky Mountain spotted fever and typhus fever. They are about 0.3 µm in diameter and less than 2 µm in length. They are nonmotile and have a definite cell wall, composed of mucopeptides and are surrounded by capsular material just as in bacteria. They contain both RNA and DNA, and are stained readily by Giemsa’s stain. They reproduce by binary fission. They are found typically in arthropods and may cause diseases in man and other animals. They have yet not been cultured except in the cells of a host they infect. They are classified under bacteria.
• Pure cultures of bacteria were fIrst obtained by J. Lister in 1878 by serial dilutions in liquid media and he named the organism Bacterium lactis.
• Archebacteria are the ancient group of bacteria living in extreme environments. Some are anaerobic and produce. methane and are .called methanogens. They are found in marshes and cattle rumen. In cattle rumen they ferment cellulose. In biogas ferment¬ers they produce methane. Some live in strong brjne and are called halophiles. Some are found in hot acidic sulphur springs as aerobes and anaerobes and they are called thermoacidophiles. Their cell wall consists of polysaccharides and proteins {no pep-tidoglycans). Archebacterial cell membrane contains branched chain lipids which make them heat and acid resistant.
• The term ‘antibiotic’ was coined by Selman Waksman in 1942. Antibiotic is a substance produced by a micro-organism that inhibits the growth of other microorganisms or kills them. Some antibiotics are known as broad spectrum antibiotics because of their ability to act on several pathogenic species.
PLANT DISEASES
Disease Pathogen
1. Citrus canker = Xanthomonas citri
2. Common blight of beans = Xanthomonas phaseoli
3. Crown gall = Agrobcicterium tumefaciens
4. Ear rot of wheat = Corynebacterium tritici
5. Fire blight of apple and pear = Erwinia amylovora
6. Red stripe of sugarcane = Xanthomonas mbrilineans
7. Soft rot of carrots & turnips = Erwinia carotovora
8. Wilt disease or brown rot of potato = Pseudomonas solanaceamm
ANIMAL DISEASES
Disease Pathogen
1. Anthrax = Bacillus anthracis (G+)
2. Cholera = Vibrio cholerae (G-)
3. Diphtheria = Corynebacterium diphtheriae
4. Gonorrhoea = Neisseria gonorrhoeae
5. Leprosy = Mycobacterium leprae
6. Plague = Yersinia pestis
7. Pneumonia = Pneumococcus pneumoniae
8. Syphilis = Treponema pallidum
9. Tetanus or lock jaw = Clm'tridium -tetani
10.. Tuberculosis = Mycobacterium tuberculosis
11. Typhoid = Salmonella typhi
FUNGI
IMPORTANT POINTS TO REMEMBER
• Fungi, in which entire plant body is converted into reproductive structure, are called holocarpie, e.g., Synchitrium.
• Majority of fungi in which only a part of thallus is utilised in the formation or reproductive structure are called eucarpic, e.g. Mucor, Albugo, etc.
• Flemming (1929) extracted first antibiotic Penicillin from Penicillium notatum.
• Alcoholic fermentation is brought about chiefly by yeasts.
• Rust of wheat is caused by Puccinia spp
• Smut of several crops is caused by Ustilago spp.
• Early blight of potato is caused by Alternaria solani.
• Late blight of potato is caused by Phytophthora infestans.
• Ring worm is. caused by a fungus Microsporum sp.
• Some of the edible fungi are : Agaricus campestris, Podaxon podaxis, Lycoperdon, Clavaria and Morchella ( commonly called guchhi)
• Some mushrooms and toad stools are fattly poisonous, e.g, Amanita.
• Red rot of sugarcane is caused by Colletotrichum falcatum.
• Leaf spot disease of rice is caused by Helminthosporium.
• Leaf spots of crucifers are caused by Alternaria.
• Wilt of arhar (Cajanus) is caused by Fusarium.
• ‘Damaging off’ of seedlings is caused by Pythium.
• White rust of crucifers is caused by Albugo.
• ‘Green ear’ disease of bajra is caused by Sclerospora graminicola.
• ‘Downy mildew’ is caused by Peronospora, Sclerospora, Peronosclerospora; Plasmopara (belonging to Phycomycetes).
• ‘Powdery mildew’ is caused by Erysiphe, Uncinula, Podosphaera, etc. (belonging to Ascomycetes).
• ‘Citrus Canker’ is a disease caused bybacteria Xanthomonas citri.
• The fungus completing its life cycle on two unrelated hosts is called heteroecious, e.g., Puccinia.
• In Ascomycetes mycelium is usually branched and septate". Septa are perforated by simple pores. Sexual reproduction occurs usually by the formation of antheridia and ascogonia. After fertilization, ascogonium gives rise to number of ascogenous hyphae which by crozier formation develop ascus mother cells where karyogamy and reduction division occur to form ascospores within the ascus.
• In Basidiomycetes mycelium is branched and septate. Septa are perforated by characteristic pores called dolipore. Basidiospores are uninucleate and are produced outside the basidia.
• In some filamentous fungi, the hyphae produce small rounded or oval thin-walled segments called oidia.
• Some higher fungi have dark brown root-like structures which are called rhizomorphs. These structures serve for perennation e.g. Annellaria mellea.
• Sclerotia are hard resistant perennating structures formed by dense mass of thick¬ walled hyphae in some fungi like Claviceps purpurea. Sclerotia contain ergot which is used to check haemorrhage during child birth.
• In Aspergillus, conidiophores are unbranched and arise from specialised cells called foot cells. Conidia are borne on bottle shaped sterigmata.
• In Ascomycetes the dikaryophase is" represented by binucleate cells of the ascogo¬nium, ascogenous hyphae and the ascus mother cells.
• Red or pink bread mould (Neurospora) was discovered by Shear and Dodge (1927) and made it as an ideal organism for the study of laws of inheritance. Later on Beadle and Tatum (1941), both Nobel Prize winners of 1958, discovered biochemical muta¬tions in Neurospora crassa. On the basis of their studies, they proposed one gene one enzyme concept which means that a gene exerts its influence on the phenotype through its role in production of, an enzyme. Neurospora is a haploid fungus, and in the absence of allele, each gene is expressed, irrespective of whether it is dominant or recessive. Thus it permits detailed analysis of crossing over.
• The mycelium, with one nucleus in cell is called monokaryotic, with binucleate cells known as dikaryotic where each nucleus is usually derived from a different parent cell. The process by which the dikaryotic condition is established is called dikaryotiza¬tion or diploidization which is found in Basidiomycetes. The dikaryotic mycelium is often called secondary mycelium which is characterised by the presence of bridge-like hyphal connections, called clamp connections, formed during cell division and func¬tion as by-pass hyphae, through which migration of one of the sister nuclei formed from a nucleus of a dikaryotic pair to the adjacent cell occurs.
• Ascomycetes produce their asci, contairiing ascospores in fruiting bodies called ascocarps. When the ascocarp is more or less rounded, completely closed, it is called cleistotbedum as in Aspergillus and Penicillium. Saucer or cup-shaped ascocarp with wide opening is called apotbecium as in Ascobolus. The flask-like ascocarp is called peritbecium which is perforated at the apex by a pore, called ostiole as in Venturia. When ascocarp is boat-shaped, it is called histerotbecium as in Glonium.
• Parasexuality is a process, in which plasmogamy, karyogamy and reduction division take place but not at specified points in the thallus or in the life cycle as in Aspergillus nidulans, the imperfect stage of Emericella nidulans where this phenomenon was first reported by Poutecorvo and Roper (1952).
• Various species of Penicillium are commonly known as green or blue moulds. Penicillium usually grows as a saprophyte on decaying fruits and vegetables. The conidiophores of this fungus are branched in a broom like manner in the upper portion. This brush-like. portion of the conidiophore is called penicillus, hence the name Pen-icillium. As a result of sexual reproduction, a fruiting body called Cleistothecium is formed.
• Ustilago, a member of Basidiomycetes group of fungi, causes smut diseases of a num-ber of cereal crops. Smut diseases receive this name from the black dusty masses of spores often called soot or smut. Some examples of smut diseases of the cereals are loose smut of wheat and barley (caused by Ustilago nuda), loose smut of corn (caused by U. maydis), covered smut of barley (caused by U. hordei), smut of sugarcane (caused by U. scitaminea) etc. The fungus produces two types of spores- (i) Smut or brand spores or Chlamydospores or teleutospores (single celled and binucleate in the beginning but later on become uninucleate by the fusion of two nuclei) and (ii) basid- iospores (haploid).
• Puccinia, another member of Basidiomycetes group of fungi, causes rust disease of many crop plants. It is a macrocyclic and generally heteroecious rust (completing life cycle on two different hosts). The rust or wheat is of three types caused by different species of Puccinia. (i) Black rust of wheat is caused by Puccinia graminis tritici. It produces single-celled uredeniospores and bi-celled teleutospores on wheat plant, and Pycnidiospores (spermatia) on the upper surface of the leaf and aecidiospres or aeciospores on the lower surface of the leaf of barberry (Berberis vulgaris) or Mahonia (alternate hosts). (ii) Yellow or stripe rust of wheat is caused by Puccinia striiformis. It is also heteroecious rust but no alternate host is known so far. (iii) Leaf or brown rust of wheat is caused by Puccinia recondita. Its alternate host is Thalictrum flavum.
• There is annual recurrence of rust in plains of India, the cause of which was first studied by late Dr. K.C. Mehta (1931).
• The fungi growing on dung of animals are called coprophilous e.g. Ascobolus, Pilobolus.
• The club root disease of cabbage (crucifers) is caused by Plasmodiophora brassicae.
• Damping off seedling and root rot is caused by Pythium.
• Late light of Patato is caused by Phytophthora infestans while early bljght is caused by Alternana solani.
• In Pilobolus the sporangia are violently thrown off towards light upto a distance of 2 metres, so this fungus is also called a 'shoot gun fungus' or 'hat thrower fungus'.
• Powdery mildew is caused by Erysiphe, Uncinula etc. and downy mildew is caused by Peronospora and Plasmopara.
• White rust of crucufers is caused by Albugo sp.
• The characteristtc feature of Basidiomycetes mycellum is the presence of dolipore septum. The septum has a barrel-shaped pore and the pore on the two sides is sur-rounded by a cap-like structure called the parenthesome or nuclear pore cap.
• Mushrooms and Toadstools also called gill fungi have umbrella-likr fruiting bodies. Agaricus is edible while Amanita is poisonous.
• Psilocybe ‘sacred mushroom’ produces Psilocybin a hallucinogenic chemical.
• Polyporus is a wood rotting fungus i.e. it is epixylic.
• Brown leaf spot of rice is caused by Helminthosporium oryzae.
• Bordeaux mixture -is the most extensively used fungicide throughout the world and was discovered by Prof. Millardet (1882). It is a common mixture of CuSO4 (4lb), quicklime (4 lb) and water (50 gallons).
• Predaceous fungi are the animal-trapping fungi (e.g. Arthrobotrys, Dactylella, Dactylaria etc.), belonging to the Deuteromycetes group, which capture small animals such as eelworms, rotifers or protozoans and use them as food.
• Fairy ring is a ring of mushrooms on the ground representing the periphery of mycelial growth of the fungus.
• Majority of lichens have fungal component belonging to Ascomycetes and hence called Ascolichens, e.g. Parmelia, Physcia, Lecanora, Buellia, Cladonia, Usnea, etc.
• Basidiolichens are rare e.g. Cora.
• The common asexual reproductive bodies in lichens are the soredia and isidia.
• Plant quarantine may be defined as a legal restriction on the movement of any in¬fected plant material for the purpose of exclusion, prevention or delay in the spread of plant pests and diseases in uninfested areas.
• In endomycorrhiza the fungal hyphae occur between and within the cells of cortex. There is a form of endotrophic mycorrhiza in which fungus lives between the cells of cortex and forms temporary hyphal projections that penetrate the cortical cells. These are called vesicular arbuscular mycorrhizae (VAM) which are important in phosphate nutrition of plants.
• Chiastobasidium is found in Cantharellus (Hymenomycetes, Basidiomycotina) Basidia are termed differently on the basis of the location of the diploid nucleus and orientation of the spindle during meiosis.
In stichic basidia (Stichobasidia) the diploid nucleus lies in the centre and the spindle lies in the longitudinal direction with respect to the basidium.
If the nucleus lies in the apical region and the spindle is oriented at right angles to the axis the basidium is termed as chiastic basidium or chisatobasidium .
• Fungi Olpidium ( Chytidiomycetes, Mastigomycotina) was first report to be involved in transmission of viral disease.
Olpidium brassicae serves as vector of at least three viruses in soil viz. lettuce big vein virus (BVV), tobacco necrosis virus (TNV) and tobacco stunt virus (TSV). The viruses are disseminated by zoospores and survive in the resting spores for several months.
• ‘St. Anthony’s fire’ or ‘Holy fire’ disease or condition is caused by eating rye (Secale cereale) flour contaminated by ergot alkaloids. In this disease fingers, toes, whole arms, legs, ears or nose become gangrenous and fall off with no bleeding. This was very common during feudal days in Europe.
• Sporangium of Stemonites (Myxomycetes) contains capillitium.
• Systemic fungicide- Benlate, Mancozeb, Dithane M-45
• In Basidiomycetes angiocarpous fructification is found in Lycoperdon.
• Dimorphism is a characteristic feature of some of the fungi- Achlya. (The term dimorphism is used when two types of zoospores (Primary and Secondary) are found in the life cycle.
• Dikaryotization in Puccinia graminis was first reported by Craigie, J.H.
• In Albugo candida oogonial wall is fused with oospore wall.
• Cyathus is known as Bird’s Nest Fungi
• Cystidia, which are sterile, generally light coloured and conial organs are met within the fruiting body of Psalito. (?)
• Phytoalexins are certain phenolic substances produced by host to kill the pathogens
• The fungus without mycelium is Saccharomyces
• Amatoxin, cephalotoxin and aflatoxin are of fungal origin, but capsaicin is not of fungal origin
• Fungus Cordyceps is parasite on insects.
• Dipilanetism is found in fungus Saprolegnia.
• Parasexuality was first reported by Pontecarvo and Roper.
• Torula condition may be obtained in Mucor.
• Fruit body of fungus Polystictus is luminescent.
• Fusarium moniliforme is associated with the discovery of Gibberllins.
• Sclerotium of fungus Claviceps produces apothecium after germination.
• In Erysiphe graminis branched haustorium is found
• Fusarium produces a sporodochium ?
• K.O. Muller proposed the role of phytoalexin in disease resistance
• Phytoalexin were first reported by Muller (1940)
• L.S.D. is obtained from Claviceps.
• Oospores are found in Phytopthora.
• Brachymeiosis is related to Yeast.
• Epidemiology is the study of – disease development in population of plants, spread of disease and management of disease.
• Coprophilous fungus – Agaricus
• Chlamydospores are found in smuts.
• Members of Ascomycotina are commonly known as Sac Fungi.
• The fertile layer bearing asci or basidia is named Hymenium.
• Perfect stage of Aspergillus – Emericella
• Vesicular Arbuscular Mycorrhiza in plant roots is produced by – Glomus
• Hyphal wall of Mucorales is composed of – Chitosan
• The fungi Tuber melanospermum is used as food.
• Facultative parasite – Pythium
• An Indian rust specialist who brought fame to India by his researches was – K.C. Mehta.
• The best method for the control of plant disease is – use of resistant varieties
• The fungi found useful in the biological control of plant diseases – Trichoderma viridae
• Aseptate mycelium – Albugo
• Powdery mildew are includd in – Ascomycetes
• Rhizopus – Bread mold
• Bacillus thuringiensis is used as microbial insecticide (Biopesticide) (biocontrol of insect pest of crops)
• The maximum permissible amount of a pesticide present in milligrams per kilograms of food product which is harmless to consumers is known as Tolerance level
• Vapam is not a volatile soil treating element ( Nitrobenzene, Methyl bromide, Chloropicrin)
• Saprolegnia an aquatic fungus is a parasite on eggs and gills of fishes.
•
TELIOMYCETES
(a) Uridinales ( Rust fungi)
(b) Ustilaginals (Smut fungi)
Rust
• In some filamentous fungi, the hyphae produce small rounded or oval thin walled segments called oidia.
• Some higher fungi have dark brown root-like structures which are called rhizomorphs. These structure serve for perennation e.g. Armellaria mellea.
• Sclerotia are hard resistant perennating structure formed by dense mass of thick walled hyphae in some fungi like Claviceps purpurea.
• In Aspergillus, conidiophores are unbranched and arise from specialized cells called foot cells.
• In ascomycetes the dikaryophase is represented by binucleate cells of t he ascogonium, ascogenous hyphae and the ascus mother cells.
• Red of pink bread mould (Neurospora) was discovered by Shear and Dodge (1927) and made it as an ideal organism for the study of laws of inheritance. Later on Beadle and Tatum (1941), both Nobel Prize winners of 1958, discovered biochemical mutations in Neurospora crassa. On the basis of their studies, they proposed one gene one enzyme concept which means that a gene exerts its influence on the phenotype through its role in production of an enzyme. Neurospora is haploid fungus, and in the absence of allele, each gene is expressed, irrespective of whether it is dominant or recessive. Thus it permits details analysis of crossing over.
• The mycelium, with only one nucleus in cell is called monokaryotic, with binucleate cells known as dikaryotic where each nucleus is usually derived from a different parent cell. The process by which the dikaryotic condition is established is called dikaryotization ofr diploidization which is found in Basidiomycetes.The dikaryotic mycelium is often called secondary mycelium which is characterized by the presence of bridge-like hyphal connections, called clamp connections, formed during cell division and function as by-pass hyphae, t hrough which migration of one of the siser nuclei formed from a nucleus of a dikaryotic pair to the adjacent cell occurs.
• Ascomycetes produce their asci, containing ascospores in fruiting bodies called ascocarps. When the ascocarp is more or less rounded, completely closed, it is called cleistothecium as in Aspergillus and Penicillium. Saucer of cup-shaped ascocarp with wide opening is called apothecium as in Ascobolus. The flask- like ascocarp is called perithecium which is perforated at the apex by a pore, called outiole as in Venturia. When ascocarp is boat-shaped, it is called histerothecium as in Glonium.
• Parasexuality is a process, in which plasmogamy, karyogamy and reduction division take place but not at specified points in the thallus of in the life cycle as in Aspergillus nidulans, the imperfect stage of Emericella nidulans where this phenomenon was first reported by Ponetcorvo and Roper (1952).
• Various species of Penicillium are commonly known as green or blue moulds. Penicillium usually grows as a saprophyte on decaying fruits and vegetables. The conidiophores of this fungus are branched in a broom like manner in the upper portion. This brush-like portion of the conidiophore is called penicillus, hence the name Penicillium. As a result of sexual reproduction, a fruiting body called cleistothecium is formed.
• Ustilago, a member of Basidiomycetes group of fungi, causes smut diseases of a number of cereal crops. Smut diseases receive this name from the black dusty masses of spores foten called soot of smut. Some examples of smut diseases of the cereals are loose smut of wheat and barley (caused by Ustilao nuda), loose smut of corn (caused by U. maydis), covered smut of barley (caused by U. hordei), smut of sugarcane (caused by U. scitaminea) etc. The fungus produces two types of spores-(i) Smut of brand spores of Chlamydospores of teleutospores (single celled and binucleate in the beginning but later on become uninucleate by the fusion of two nuclei) and ( ii) basidiospores (haploid).
Amanita (Hymenomycetes, Basidiomycotina)
Amanita phalloides ‘Death chair’ or ‘death cap’ Extremely poisonous. Phallodin is a poisonous substance of Amanita phalloides.
Amanita verna Destroying angel
Amanita pantherina Panther cap
Amanita muscaria Fly fungus, causes hallucination
Three toxins- α-amanitine, β-amanitine & phalloidin
A. muscaria- two poisonous chemicals: muscarine, muscaridine
Amanita has a hallucinogenic property.
Disease caused by Algae Causal organism/ Algae
Red rust of tea Cephaleuros
Fungal diseases of human beings Causal organisms
Ring worm (tinea) Epidermophyton spp.
Ring worm Microsporum sp., Trichophyton sp.
Ring worm (tinea) Trichophyton spp.
Athelete's foot Trichophyton sp.
Candidiasis Candida albicans
Hey fewer (allergy) Alternaria, Monilia, Trichoderma etc.
Bacterial Diseases of Plants Causal organisms/ Bacteria
Angular leaf spot disease Xanthomonas malvacearum
Crown gall disease Agrobacterium tumifaciens
Hairy root diseaes A. rhizogens
Firer blight of Apple Bacterial pathogen
Potato spindle tuber viroid VIROIDS viroid
Watery stipe disease of mushroom VIRUS virus
P.A. Micheli Founder or Father of Mycology
E.M. Fries Linnaeus of Mycology or Father of systematic Mycology
H.A. de Bary Father of Modern Mycology and Father of Plant Pathology
Sir E.J. Butler Father of Indian Mycology, Father of Indian Plant Pathology
• Fungi, in which entire plant body is converted into reproductive structure, are called holocarpie, e.g., Synchitrium.
• Majority of fungi in which only a part of thallus is utilised in the formation or reproductive structure are called eucarpic, e.g. Mucor, Albugo, etc.
• Flemming (1929) extracted first antibiotic Penicillin from Penicillium notatum.
• Alcoholic fermentation is brought about chiefly by yeasts.
• Rust of wheat is caused by Puccinia spp
• Smut of several crops is caused by Ustilago spp.
• Early blight of potato is caused by Alternaria solani.
• Late blight of potato is caused by Phytophthora infestans.
• Ring worm is. caused by a fungus Microsporum sp.
• Some of the edible fungi are : Agaricus campestris, Podaxon podaxis, Lycoperdon, Clavaria and Morchella ( commonly called guchhi)
• Some mushrooms and toad stools are fattly poisonous, e.g, Amanita.
• Red rot of sugarcane is caused by Colletotrichum falcatum.
• Leaf spot disease of rice is caused by Helminthosporium.
• Leaf spots of crucifers are caused by Alternaria.
• Wilt of arhar (Cajanus) is caused by Fusarium.
• ‘Damaging off’ of seedlings is caused by Pythium.
• White rust of crucifers is caused by Albugo.
• ‘Green ear’ disease of bajra is caused by Sclerospora graminicola.
• ‘Downy mildew’ is caused by Peronospora, Sclerospora, Peronosclerospora; Plasmopara (belonging to Phycomycetes).
• ‘Powdery mildew’ is caused by Erysiphe, Uncinula, Podosphaera, etc. (belonging to Ascomycetes).
• ‘Citrus Canker’ is a disease caused bybacteria Xanthomonas citri.
• The fungus completing its life cycle on two unrelated hosts is called heteroecious, e.g., Puccinia.
• In Ascomycetes mycelium is usually branched and septate". Septa are perforated by simple pores. Sexual reproduction occurs usually by the formation of antheridia and ascogonia. After fertilization, ascogonium gives rise to number of ascogenous hyphae which by crozier formation develop ascus mother cells where karyogamy and reduction division occur to form ascospores within the ascus.
• In Basidiomycetes mycelium is branched and septate. Septa are perforated by characteristic pores called dolipore. Basidiospores are uninucleate and are produced outside the basidia.
• In some filamentous fungi, the hyphae produce small rounded or oval thin-walled segments called oidia.
• Some higher fungi have dark brown root-like structures which are called rhizomorphs. These structures serve for perennation e.g. Annellaria mellea.
• Sclerotia are hard resistant perennating structures formed by dense mass of thick¬ walled hyphae in some fungi like Claviceps purpurea. Sclerotia contain ergot which is used to check haemorrhage during child birth.
• In Aspergillus, conidiophores are unbranched and arise from specialised cells called foot cells. Conidia are borne on bottle shaped sterigmata.
• In Ascomycetes the dikaryophase is" represented by binucleate cells of the ascogo¬nium, ascogenous hyphae and the ascus mother cells.
• Red or pink bread mould (Neurospora) was discovered by Shear and Dodge (1927) and made it as an ideal organism for the study of laws of inheritance. Later on Beadle and Tatum (1941), both Nobel Prize winners of 1958, discovered biochemical muta¬tions in Neurospora crassa. On the basis of their studies, they proposed one gene one enzyme concept which means that a gene exerts its influence on the phenotype through its role in production of, an enzyme. Neurospora is a haploid fungus, and in the absence of allele, each gene is expressed, irrespective of whether it is dominant or recessive. Thus it permits detailed analysis of crossing over.
• The mycelium, with one nucleus in cell is called monokaryotic, with binucleate cells known as dikaryotic where each nucleus is usually derived from a different parent cell. The process by which the dikaryotic condition is established is called dikaryotiza¬tion or diploidization which is found in Basidiomycetes. The dikaryotic mycelium is often called secondary mycelium which is characterised by the presence of bridge-like hyphal connections, called clamp connections, formed during cell division and func¬tion as by-pass hyphae, through which migration of one of the sister nuclei formed from a nucleus of a dikaryotic pair to the adjacent cell occurs.
• Ascomycetes produce their asci, contairiing ascospores in fruiting bodies called ascocarps. When the ascocarp is more or less rounded, completely closed, it is called cleistotbedum as in Aspergillus and Penicillium. Saucer or cup-shaped ascocarp with wide opening is called apotbecium as in Ascobolus. The flask-like ascocarp is called peritbecium which is perforated at the apex by a pore, called ostiole as in Venturia. When ascocarp is boat-shaped, it is called histerotbecium as in Glonium.
• Parasexuality is a process, in which plasmogamy, karyogamy and reduction division take place but not at specified points in the thallus or in the life cycle as in Aspergillus nidulans, the imperfect stage of Emericella nidulans where this phenomenon was first reported by Poutecorvo and Roper (1952).
• Various species of Penicillium are commonly known as green or blue moulds. Penicillium usually grows as a saprophyte on decaying fruits and vegetables. The conidiophores of this fungus are branched in a broom like manner in the upper portion. This brush-like. portion of the conidiophore is called penicillus, hence the name Pen-icillium. As a result of sexual reproduction, a fruiting body called Cleistothecium is formed.
• Ustilago, a member of Basidiomycetes group of fungi, causes smut diseases of a num-ber of cereal crops. Smut diseases receive this name from the black dusty masses of spores often called soot or smut. Some examples of smut diseases of the cereals are loose smut of wheat and barley (caused by Ustilago nuda), loose smut of corn (caused by U. maydis), covered smut of barley (caused by U. hordei), smut of sugarcane (caused by U. scitaminea) etc. The fungus produces two types of spores- (i) Smut or brand spores or Chlamydospores or teleutospores (single celled and binucleate in the beginning but later on become uninucleate by the fusion of two nuclei) and (ii) basid- iospores (haploid).
• Puccinia, another member of Basidiomycetes group of fungi, causes rust disease of many crop plants. It is a macrocyclic and generally heteroecious rust (completing life cycle on two different hosts). The rust or wheat is of three types caused by different species of Puccinia. (i) Black rust of wheat is caused by Puccinia graminis tritici. It produces single-celled uredeniospores and bi-celled teleutospores on wheat plant, and Pycnidiospores (spermatia) on the upper surface of the leaf and aecidiospres or aeciospores on the lower surface of the leaf of barberry (Berberis vulgaris) or Mahonia (alternate hosts). (ii) Yellow or stripe rust of wheat is caused by Puccinia striiformis. It is also heteroecious rust but no alternate host is known so far. (iii) Leaf or brown rust of wheat is caused by Puccinia recondita. Its alternate host is Thalictrum flavum.
• There is annual recurrence of rust in plains of India, the cause of which was first studied by late Dr. K.C. Mehta (1931).
• The fungi growing on dung of animals are called coprophilous e.g. Ascobolus, Pilobolus.
• The club root disease of cabbage (crucifers) is caused by Plasmodiophora brassicae.
• Damping off seedling and root rot is caused by Pythium.
• Late light of Patato is caused by Phytophthora infestans while early bljght is caused by Alternana solani.
• In Pilobolus the sporangia are violently thrown off towards light upto a distance of 2 metres, so this fungus is also called a 'shoot gun fungus' or 'hat thrower fungus'.
• Powdery mildew is caused by Erysiphe, Uncinula etc. and downy mildew is caused by Peronospora and Plasmopara.
• White rust of crucufers is caused by Albugo sp.
• The characteristtc feature of Basidiomycetes mycellum is the presence of dolipore septum. The septum has a barrel-shaped pore and the pore on the two sides is sur-rounded by a cap-like structure called the parenthesome or nuclear pore cap.
• Mushrooms and Toadstools also called gill fungi have umbrella-likr fruiting bodies. Agaricus is edible while Amanita is poisonous.
• Psilocybe ‘sacred mushroom’ produces Psilocybin a hallucinogenic chemical.
• Polyporus is a wood rotting fungus i.e. it is epixylic.
• Brown leaf spot of rice is caused by Helminthosporium oryzae.
• Bordeaux mixture -is the most extensively used fungicide throughout the world and was discovered by Prof. Millardet (1882). It is a common mixture of CuSO4 (4lb), quicklime (4 lb) and water (50 gallons).
• Predaceous fungi are the animal-trapping fungi (e.g. Arthrobotrys, Dactylella, Dactylaria etc.), belonging to the Deuteromycetes group, which capture small animals such as eelworms, rotifers or protozoans and use them as food.
• Fairy ring is a ring of mushrooms on the ground representing the periphery of mycelial growth of the fungus.
• Majority of lichens have fungal component belonging to Ascomycetes and hence called Ascolichens, e.g. Parmelia, Physcia, Lecanora, Buellia, Cladonia, Usnea, etc.
• Basidiolichens are rare e.g. Cora.
• The common asexual reproductive bodies in lichens are the soredia and isidia.
• Plant quarantine may be defined as a legal restriction on the movement of any in¬fected plant material for the purpose of exclusion, prevention or delay in the spread of plant pests and diseases in uninfested areas.
• In endomycorrhiza the fungal hyphae occur between and within the cells of cortex. There is a form of endotrophic mycorrhiza in which fungus lives between the cells of cortex and forms temporary hyphal projections that penetrate the cortical cells. These are called vesicular arbuscular mycorrhizae (VAM) which are important in phosphate nutrition of plants.
• Chiastobasidium is found in Cantharellus (Hymenomycetes, Basidiomycotina) Basidia are termed differently on the basis of the location of the diploid nucleus and orientation of the spindle during meiosis.
In stichic basidia (Stichobasidia) the diploid nucleus lies in the centre and the spindle lies in the longitudinal direction with respect to the basidium.
If the nucleus lies in the apical region and the spindle is oriented at right angles to the axis the basidium is termed as chiastic basidium or chisatobasidium .
• Fungi Olpidium ( Chytidiomycetes, Mastigomycotina) was first report to be involved in transmission of viral disease.
Olpidium brassicae serves as vector of at least three viruses in soil viz. lettuce big vein virus (BVV), tobacco necrosis virus (TNV) and tobacco stunt virus (TSV). The viruses are disseminated by zoospores and survive in the resting spores for several months.
• ‘St. Anthony’s fire’ or ‘Holy fire’ disease or condition is caused by eating rye (Secale cereale) flour contaminated by ergot alkaloids. In this disease fingers, toes, whole arms, legs, ears or nose become gangrenous and fall off with no bleeding. This was very common during feudal days in Europe.
• Sporangium of Stemonites (Myxomycetes) contains capillitium.
• Systemic fungicide- Benlate, Mancozeb, Dithane M-45
• In Basidiomycetes angiocarpous fructification is found in Lycoperdon.
• Dimorphism is a characteristic feature of some of the fungi- Achlya. (The term dimorphism is used when two types of zoospores (Primary and Secondary) are found in the life cycle.
• Dikaryotization in Puccinia graminis was first reported by Craigie, J.H.
• In Albugo candida oogonial wall is fused with oospore wall.
• Cyathus is known as Bird’s Nest Fungi
• Cystidia, which are sterile, generally light coloured and conial organs are met within the fruiting body of Psalito. (?)
• Phytoalexins are certain phenolic substances produced by host to kill the pathogens
• The fungus without mycelium is Saccharomyces
• Amatoxin, cephalotoxin and aflatoxin are of fungal origin, but capsaicin is not of fungal origin
• Fungus Cordyceps is parasite on insects.
• Dipilanetism is found in fungus Saprolegnia.
• Parasexuality was first reported by Pontecarvo and Roper.
• Torula condition may be obtained in Mucor.
• Fruit body of fungus Polystictus is luminescent.
• Fusarium moniliforme is associated with the discovery of Gibberllins.
• Sclerotium of fungus Claviceps produces apothecium after germination.
• In Erysiphe graminis branched haustorium is found
• Fusarium produces a sporodochium ?
• K.O. Muller proposed the role of phytoalexin in disease resistance
• Phytoalexin were first reported by Muller (1940)
• L.S.D. is obtained from Claviceps.
• Oospores are found in Phytopthora.
• Brachymeiosis is related to Yeast.
• Epidemiology is the study of – disease development in population of plants, spread of disease and management of disease.
• Coprophilous fungus – Agaricus
• Chlamydospores are found in smuts.
• Members of Ascomycotina are commonly known as Sac Fungi.
• The fertile layer bearing asci or basidia is named Hymenium.
• Perfect stage of Aspergillus – Emericella
• Vesicular Arbuscular Mycorrhiza in plant roots is produced by – Glomus
• Hyphal wall of Mucorales is composed of – Chitosan
• The fungi Tuber melanospermum is used as food.
• Facultative parasite – Pythium
• An Indian rust specialist who brought fame to India by his researches was – K.C. Mehta.
• The best method for the control of plant disease is – use of resistant varieties
• The fungi found useful in the biological control of plant diseases – Trichoderma viridae
• Aseptate mycelium – Albugo
• Powdery mildew are includd in – Ascomycetes
• Rhizopus – Bread mold
• Bacillus thuringiensis is used as microbial insecticide (Biopesticide) (biocontrol of insect pest of crops)
• The maximum permissible amount of a pesticide present in milligrams per kilograms of food product which is harmless to consumers is known as Tolerance level
• Vapam is not a volatile soil treating element ( Nitrobenzene, Methyl bromide, Chloropicrin)
• Saprolegnia an aquatic fungus is a parasite on eggs and gills of fishes.
•
TELIOMYCETES
(a) Uridinales ( Rust fungi)
(b) Ustilaginals (Smut fungi)
Rust
• In some filamentous fungi, the hyphae produce small rounded or oval thin walled segments called oidia.
• Some higher fungi have dark brown root-like structures which are called rhizomorphs. These structure serve for perennation e.g. Armellaria mellea.
• Sclerotia are hard resistant perennating structure formed by dense mass of thick walled hyphae in some fungi like Claviceps purpurea.
• In Aspergillus, conidiophores are unbranched and arise from specialized cells called foot cells.
• In ascomycetes the dikaryophase is represented by binucleate cells of t he ascogonium, ascogenous hyphae and the ascus mother cells.
• Red of pink bread mould (Neurospora) was discovered by Shear and Dodge (1927) and made it as an ideal organism for the study of laws of inheritance. Later on Beadle and Tatum (1941), both Nobel Prize winners of 1958, discovered biochemical mutations in Neurospora crassa. On the basis of their studies, they proposed one gene one enzyme concept which means that a gene exerts its influence on the phenotype through its role in production of an enzyme. Neurospora is haploid fungus, and in the absence of allele, each gene is expressed, irrespective of whether it is dominant or recessive. Thus it permits details analysis of crossing over.
• The mycelium, with only one nucleus in cell is called monokaryotic, with binucleate cells known as dikaryotic where each nucleus is usually derived from a different parent cell. The process by which the dikaryotic condition is established is called dikaryotization ofr diploidization which is found in Basidiomycetes.The dikaryotic mycelium is often called secondary mycelium which is characterized by the presence of bridge-like hyphal connections, called clamp connections, formed during cell division and function as by-pass hyphae, t hrough which migration of one of the siser nuclei formed from a nucleus of a dikaryotic pair to the adjacent cell occurs.
• Ascomycetes produce their asci, containing ascospores in fruiting bodies called ascocarps. When the ascocarp is more or less rounded, completely closed, it is called cleistothecium as in Aspergillus and Penicillium. Saucer of cup-shaped ascocarp with wide opening is called apothecium as in Ascobolus. The flask- like ascocarp is called perithecium which is perforated at the apex by a pore, called outiole as in Venturia. When ascocarp is boat-shaped, it is called histerothecium as in Glonium.
• Parasexuality is a process, in which plasmogamy, karyogamy and reduction division take place but not at specified points in the thallus of in the life cycle as in Aspergillus nidulans, the imperfect stage of Emericella nidulans where this phenomenon was first reported by Ponetcorvo and Roper (1952).
• Various species of Penicillium are commonly known as green or blue moulds. Penicillium usually grows as a saprophyte on decaying fruits and vegetables. The conidiophores of this fungus are branched in a broom like manner in the upper portion. This brush-like portion of the conidiophore is called penicillus, hence the name Penicillium. As a result of sexual reproduction, a fruiting body called cleistothecium is formed.
• Ustilago, a member of Basidiomycetes group of fungi, causes smut diseases of a number of cereal crops. Smut diseases receive this name from the black dusty masses of spores foten called soot of smut. Some examples of smut diseases of the cereals are loose smut of wheat and barley (caused by Ustilao nuda), loose smut of corn (caused by U. maydis), covered smut of barley (caused by U. hordei), smut of sugarcane (caused by U. scitaminea) etc. The fungus produces two types of spores-(i) Smut of brand spores of Chlamydospores of teleutospores (single celled and binucleate in the beginning but later on become uninucleate by the fusion of two nuclei) and ( ii) basidiospores (haploid).
Amanita (Hymenomycetes, Basidiomycotina)
Amanita phalloides ‘Death chair’ or ‘death cap’ Extremely poisonous. Phallodin is a poisonous substance of Amanita phalloides.
Amanita verna Destroying angel
Amanita pantherina Panther cap
Amanita muscaria Fly fungus, causes hallucination
Three toxins- α-amanitine, β-amanitine & phalloidin
A. muscaria- two poisonous chemicals: muscarine, muscaridine
Amanita has a hallucinogenic property.
Disease caused by Algae Causal organism/ Algae
Red rust of tea Cephaleuros
Fungal diseases of human beings Causal organisms
Ring worm (tinea) Epidermophyton spp.
Ring worm Microsporum sp., Trichophyton sp.
Ring worm (tinea) Trichophyton spp.
Athelete's foot Trichophyton sp.
Candidiasis Candida albicans
Hey fewer (allergy) Alternaria, Monilia, Trichoderma etc.
Bacterial Diseases of Plants Causal organisms/ Bacteria
Angular leaf spot disease Xanthomonas malvacearum
Crown gall disease Agrobacterium tumifaciens
Hairy root diseaes A. rhizogens
Firer blight of Apple Bacterial pathogen
Potato spindle tuber viroid VIROIDS viroid
Watery stipe disease of mushroom VIRUS virus
P.A. Micheli Founder or Father of Mycology
E.M. Fries Linnaeus of Mycology or Father of systematic Mycology
H.A. de Bary Father of Modern Mycology and Father of Plant Pathology
Sir E.J. Butler Father of Indian Mycology, Father of Indian Plant Pathology
ALGAE
IMOPORTANT POINTS TO REMEMBER
SOME POINTS
Planktons of Known as
Sea and lakes Euplanktons
Rivers and streams Potamoplanktons
Small pond or ditch Heloplankton
If the plant grow attach to term
Other plant epiphytic
animal epizoic
rock epilethic
Between cracks and crevices Chesmolithic
Found beneath the rock hyptolytic
• Phycology – Study of algae
• Indian algolist- M. O. P. Iyengar, Randhawa, Y. S. R. K. Sharma
• Smallest algae- Micromonas pusillum, 0.5m ( green algae )
• Largest algae- Macrocystis pyrifera , 80m or more in length ( brown algae )
• Carlous Linnaeus, Species Plantrum (1753), introduced first time the word ‘algae’
• Cladophora may live in symbiotic relationship with a sponge (Eplydatea fuiritalis)
• Flagella are absent in Cyanophyta, Prochlorophyta, Rhodophyta
• Cell wall in genus Tribonema (Xanthophyceae) have ‘H’ pieces. Microspora (Ulotrichales) also known for H pieces.
• Genus Protosiphon, a fresh water siphonales has similar habit like that of Botrydium but without branched rhizoids.
• Parasexuality (= genetic recombination) i.e. exchange of gene materials among the two mating cells but this recombination differs from true sexuality in the absence of meiosis or syngamy and fusion of two gametes.
• Parasexuality first reported in Anacystis nidulans by Kumar (1962), other genera Anabaena, Cylendrospermum.
• In haplontic life cycle a microorganism meiosis takes place in Zygotes.
• Flagella are absent in Cyanophyta, Prochlorophyta and Rhodophyta.
• Diatomite or diatomaceous earth is a rocklike deposit formed from the siliceous walls of past Diatoms.
• Irish moss- Chondrus crispus (a red algae)
• Sea palm- Postelsia palmaeformis (Brown algae)
CYANOPHYCEAE or MYXOPHYCEAE (Blue Green Algae)
• Blue green algae are called Cyanobacteria because they do not have nucleus.
• Nitrogenous food reserves are found in the cells of Blue Green Algae.
• Sexual reproduction does not take place in Myxophyceae
• The red colour of sea is caused by the heavy growth of Trichodesmium erythrium
• False branching is found in Scytonema.
• Aulosira fertilissima (a common nitrogen fixing species) the dominant alga of rice fields, proved to be the most powerful nitrogen fixer and “a large fraction of the nitrogen fixed was in an available form for the benefit of the rice crop.”
• The most important function of heterocyst is nitrogen fixation.
• Cyanophages from India were discovered for the first time by R.N. Singh and P.L.Singh.
• Cyanophages were discovered by Schafferman and Moris
• Some blue green algae (BGA) live in protozoans and are called cynallele.
• Cynellae- These are blue green bacterial endosymbiont of Protozoa. They are found in a Peliaina and Paulinella. Paulinella contains from one to six cynellae. The cynellae were discovered by A. Pascher in 1929.
PROCHLOROPHYCEAE
• Prochloron – Chlorooxybacteria.
• Prokaryotic algae Prochloron posses chlorophyll b.
• Genus Prochloron is first described by Lewin (1972) as an obligate symbiont inside cloacal chamber of ‘Sea Squirts’ an Ascidian.
CHLOROPHYCEAE (Green Algae)
• Chlamydomonas show all the three types of sexual reproduction i.e. isogamy, anisogamy and oogamy
• Recent electron microscopc studies on cell division and motile cells of green algae have revealed that the genera related to the origin of land plants may be- Coleochaete and Chara.
• Heterotrichous terrestrial alga – Fritschiella tuberosa
• Truly heterotrichous – Colleochaete pulvinata, Fritschiella (green algae).
• The terrestrial alga Fritschiella tuberosa was discovered by F.E. Fritsch.
• The Fritscliella is considered as an example of evolution of higher plants from algae.
• Dwarf male is found in Oedogonim.
• Algae Spirulina has the potential to be an important source of edible protein.
• A ring of multicilliate zoogonidium is found in Oedogonium.
• Spirogyra shows physiological anisogamy
• Closterium is a true placoderm desmid (Conjugales, Chlorophyceae).
• The equatorial region connecting the semicells of desmid is Isthmus.
• The cyclosis in the cytoplasm of Chara can be observed in endoplasm.
• Several species of Chara get encrusted with Calcium carbonate and become hard brittle and rough, hence commonly called “Stone worts”.
• Calcium encrustation and larvicidal properties are present in Chara.
• The biggest single celled alga is Acetabularia
• Chantransia – stage not found in green algae (chlorophyceae)
• ‘Red rust’ of tea is caused by parasitic green alga Cephaleuros.
BASCILLARIOPHYCEAE
• Navicula is a typical unicellular freshwater diatom (Pennales, Bacillariophyceae).
• Silica is essential for members of Bacillariophyceae.
• Blue-green algae (myxophyceae or cyanophyceae) have been assigned a new name Cyanobacteria.
• Dr. R.N. Singh suggested that blue green algae can be used in reclamation of usar lands. It has been found that pH of such soils fell from 9.7 to 7.6 by growing blue green algae.
• The filaments of Anabaena are unbranched, moniliform and ensheathed in gelatinous sheath. Filaments possess heterocysts and akinetes alongwith typical cyanophycean vegetative cells which bear chromoplasm containing photosynthetic lamellae and centroplasm having genetic material.
• The principal N2 fixing blue-green alga in Indian rice fields is Aulosira fertilissima. Besides this, another nitrogen fixing blue-green alga, Chlorogloea fritschii is also found in such fields. The species of Anabaena and Nostoc are known to form symbiotic association with Anthoceros, Azolla, Cycas etc. It is interesting to note that all the spe¬cies of blue green algae (e.g. Anabaena, Nostoc, Cylindrospennum, Aulosira etc.), known definitely to be nitrogen fixing, possess heterocysts (except perhaps Chlorogloea fritschii). They may possibly in some way or the other be concerneq in the mechanism of N2 fixation.
• Biofertilizers are the organisms which can bring about soil enrichment. The main sources of biofertilizers are bacteria, cyanobacteria and fungi. Cyanobacteria have been used as biofertilizers at the Indian Agriculture Research Institute (IARI) and it is reported that upto 20-30 kg/ha of nitrogen is fixed by them.
• These cyanobacteria have a potential to supply 7-8 lakh tonnes of fixed nitrogen, equivalent to 15-17 lakh tonnes of urea, sufficient to meet the entire rice crop in our country.
CHLOROPHYCEAE ( Green algae)
• Terrestrial – Fritschiella, Chlorococcum, Oedogonium, Hormidium (Ulotrichales)
• Green algae phycobiont in lichens- Tribouxia, Tetrahedron (Chlorococcales), Trentepohilia (Chetophorales).
• Parasitic green algae- Cephaleuros ( on Magnolia, Syzygium, Tea leaves etc.)
Cephaleuros virscens ( Red rust of tea)
Rhodochytrium spilanthidis (on Ambrosia)
Phyllobium sphagnicolum (on Sphagnum, a moss)
• Endophytic –Choleochate nitellerum
Rhodochytrium
Chlorochytium
Codiolum
• Epiphytic- Choleochate, Oedogonium, Sirogonium, Characium
• Planktonic form- Cosmarium
• Epizoic- on shells of molluscs - Cladophora glomirata, Bascicladia crassa
• Endozoic- Zoochlorella (in side Hydra)
• Thermophytes- Chlorella sp.
• Cryophytes- Chlamydomonas nivalis, C. pulvalis
• Wallless green algae- Dunaliella
• In genus Carteria 4 flagella.
• Conjugales show movement by secretion of mucilage. Chlosterium aerosum shows jurky movements.
• Flagellar confugeration (9+2) exception Golenkinia (9+1), Chlamydomonas (9+0)
• Pseudocilia- Tetraspora
• Equal flagellation on anterior end, term isokontae.
• Pyrenoids are always associated with chloroplasts except in Microspora (Ulotrichales), Trentipohlia (Chetophorales)
• Isomorphic alternation of generation e.g. Ulva.
• CELL DIVISION
Phycoplast Phragmoplast
Always in algae Always in bryophytes and
Algae-Chara, Coleochate pulvinata
Zoospores are naked protoplasmic bodies which move by flagella or cilia
1. Biflagellate e.g. Ulothrix
2. Quadriflagellate – Ulothrix , Cladophora
3. Multiciliate - Oedogonium
Synzoospores – Multiciliate and multinucleate spores – Vaucheria
Aplanospores - non motile thin walled spore – Ulothrix , Chlorella
Hypnospores – thick walled, non motile spores during unfavorable condition –Ulothrix
XANTHOPHYCEAE
• In Xanthophyceae oogamy is rarely found e.g. Vaucheria
PHAEOPHYCEAE (Brown Algae)
• No unicellular forms in Phaeophyceae.
• Isomorphic alternation of generation is found in Ectocarpus.
• A male gamete with laterally inserted dimorphic flagella is found in Ectocarpus.
• Trichothallic growth is found in Ectocarpus
• Sargassum is commonly known as Gulf Weed
• The alga which exhibit gametic meiosis Sargassum.
• Sargassum has two laterally placed flagella in male gametes.
• Marine algae which is called Kelp – Laminaria.
• Sieve like cells are found in Laminaria
• Marine algae Laminaria is the chief source of alginate.
• Alginic acid derived from Brown algae (Laminaria).
• In Laminaria and Macrocystis alginic acid occurs in the middle lamellae and primary wall.
• Iodine is obtained from kelps (brown algae) e.g., Laminaria, Eisenia etc.
RHODOPHYCEAE (Red Algae)
• Rhodophyceae have one unicellular form – Porphyridium
• Alternation of generation in Polysiphonia is diplobiontic and triphasic.
• Red algae has a single thylakoid per granum
• Carpospores of Batrachospermum are: naked and nonmotile
• The site of reduction division in red algae- in Batrachospermum = carposporophyte, in Polysiphonia = tetrasporangia.
• Agar-agar is obtained from red algae such as Geledium, Gracillaria etc.
SOME POINTS
Planktons of Known as
Sea and lakes Euplanktons
Rivers and streams Potamoplanktons
Small pond or ditch Heloplankton
If the plant grow attach to term
Other plant epiphytic
animal epizoic
rock epilethic
Between cracks and crevices Chesmolithic
Found beneath the rock hyptolytic
• Phycology – Study of algae
• Indian algolist- M. O. P. Iyengar, Randhawa, Y. S. R. K. Sharma
• Smallest algae- Micromonas pusillum, 0.5m ( green algae )
• Largest algae- Macrocystis pyrifera , 80m or more in length ( brown algae )
• Carlous Linnaeus, Species Plantrum (1753), introduced first time the word ‘algae’
• Cladophora may live in symbiotic relationship with a sponge (Eplydatea fuiritalis)
• Flagella are absent in Cyanophyta, Prochlorophyta, Rhodophyta
• Cell wall in genus Tribonema (Xanthophyceae) have ‘H’ pieces. Microspora (Ulotrichales) also known for H pieces.
• Genus Protosiphon, a fresh water siphonales has similar habit like that of Botrydium but without branched rhizoids.
• Parasexuality (= genetic recombination) i.e. exchange of gene materials among the two mating cells but this recombination differs from true sexuality in the absence of meiosis or syngamy and fusion of two gametes.
• Parasexuality first reported in Anacystis nidulans by Kumar (1962), other genera Anabaena, Cylendrospermum.
• In haplontic life cycle a microorganism meiosis takes place in Zygotes.
• Flagella are absent in Cyanophyta, Prochlorophyta and Rhodophyta.
• Diatomite or diatomaceous earth is a rocklike deposit formed from the siliceous walls of past Diatoms.
• Irish moss- Chondrus crispus (a red algae)
• Sea palm- Postelsia palmaeformis (Brown algae)
CYANOPHYCEAE or MYXOPHYCEAE (Blue Green Algae)
• Blue green algae are called Cyanobacteria because they do not have nucleus.
• Nitrogenous food reserves are found in the cells of Blue Green Algae.
• Sexual reproduction does not take place in Myxophyceae
• The red colour of sea is caused by the heavy growth of Trichodesmium erythrium
• False branching is found in Scytonema.
• Aulosira fertilissima (a common nitrogen fixing species) the dominant alga of rice fields, proved to be the most powerful nitrogen fixer and “a large fraction of the nitrogen fixed was in an available form for the benefit of the rice crop.”
• The most important function of heterocyst is nitrogen fixation.
• Cyanophages from India were discovered for the first time by R.N. Singh and P.L.Singh.
• Cyanophages were discovered by Schafferman and Moris
• Some blue green algae (BGA) live in protozoans and are called cynallele.
• Cynellae- These are blue green bacterial endosymbiont of Protozoa. They are found in a Peliaina and Paulinella. Paulinella contains from one to six cynellae. The cynellae were discovered by A. Pascher in 1929.
PROCHLOROPHYCEAE
• Prochloron – Chlorooxybacteria.
• Prokaryotic algae Prochloron posses chlorophyll b.
• Genus Prochloron is first described by Lewin (1972) as an obligate symbiont inside cloacal chamber of ‘Sea Squirts’ an Ascidian.
CHLOROPHYCEAE (Green Algae)
• Chlamydomonas show all the three types of sexual reproduction i.e. isogamy, anisogamy and oogamy
• Recent electron microscopc studies on cell division and motile cells of green algae have revealed that the genera related to the origin of land plants may be- Coleochaete and Chara.
• Heterotrichous terrestrial alga – Fritschiella tuberosa
• Truly heterotrichous – Colleochaete pulvinata, Fritschiella (green algae).
• The terrestrial alga Fritschiella tuberosa was discovered by F.E. Fritsch.
• The Fritscliella is considered as an example of evolution of higher plants from algae.
• Dwarf male is found in Oedogonim.
• Algae Spirulina has the potential to be an important source of edible protein.
• A ring of multicilliate zoogonidium is found in Oedogonium.
• Spirogyra shows physiological anisogamy
• Closterium is a true placoderm desmid (Conjugales, Chlorophyceae).
• The equatorial region connecting the semicells of desmid is Isthmus.
• The cyclosis in the cytoplasm of Chara can be observed in endoplasm.
• Several species of Chara get encrusted with Calcium carbonate and become hard brittle and rough, hence commonly called “Stone worts”.
• Calcium encrustation and larvicidal properties are present in Chara.
• The biggest single celled alga is Acetabularia
• Chantransia – stage not found in green algae (chlorophyceae)
• ‘Red rust’ of tea is caused by parasitic green alga Cephaleuros.
BASCILLARIOPHYCEAE
• Navicula is a typical unicellular freshwater diatom (Pennales, Bacillariophyceae).
• Silica is essential for members of Bacillariophyceae.
• Blue-green algae (myxophyceae or cyanophyceae) have been assigned a new name Cyanobacteria.
• Dr. R.N. Singh suggested that blue green algae can be used in reclamation of usar lands. It has been found that pH of such soils fell from 9.7 to 7.6 by growing blue green algae.
• The filaments of Anabaena are unbranched, moniliform and ensheathed in gelatinous sheath. Filaments possess heterocysts and akinetes alongwith typical cyanophycean vegetative cells which bear chromoplasm containing photosynthetic lamellae and centroplasm having genetic material.
• The principal N2 fixing blue-green alga in Indian rice fields is Aulosira fertilissima. Besides this, another nitrogen fixing blue-green alga, Chlorogloea fritschii is also found in such fields. The species of Anabaena and Nostoc are known to form symbiotic association with Anthoceros, Azolla, Cycas etc. It is interesting to note that all the spe¬cies of blue green algae (e.g. Anabaena, Nostoc, Cylindrospennum, Aulosira etc.), known definitely to be nitrogen fixing, possess heterocysts (except perhaps Chlorogloea fritschii). They may possibly in some way or the other be concerneq in the mechanism of N2 fixation.
• Biofertilizers are the organisms which can bring about soil enrichment. The main sources of biofertilizers are bacteria, cyanobacteria and fungi. Cyanobacteria have been used as biofertilizers at the Indian Agriculture Research Institute (IARI) and it is reported that upto 20-30 kg/ha of nitrogen is fixed by them.
• These cyanobacteria have a potential to supply 7-8 lakh tonnes of fixed nitrogen, equivalent to 15-17 lakh tonnes of urea, sufficient to meet the entire rice crop in our country.
CHLOROPHYCEAE ( Green algae)
• Terrestrial – Fritschiella, Chlorococcum, Oedogonium, Hormidium (Ulotrichales)
• Green algae phycobiont in lichens- Tribouxia, Tetrahedron (Chlorococcales), Trentepohilia (Chetophorales).
• Parasitic green algae- Cephaleuros ( on Magnolia, Syzygium, Tea leaves etc.)
Cephaleuros virscens ( Red rust of tea)
Rhodochytrium spilanthidis (on Ambrosia)
Phyllobium sphagnicolum (on Sphagnum, a moss)
• Endophytic –Choleochate nitellerum
Rhodochytrium
Chlorochytium
Codiolum
• Epiphytic- Choleochate, Oedogonium, Sirogonium, Characium
• Planktonic form- Cosmarium
• Epizoic- on shells of molluscs - Cladophora glomirata, Bascicladia crassa
• Endozoic- Zoochlorella (in side Hydra)
• Thermophytes- Chlorella sp.
• Cryophytes- Chlamydomonas nivalis, C. pulvalis
• Wallless green algae- Dunaliella
• In genus Carteria 4 flagella.
• Conjugales show movement by secretion of mucilage. Chlosterium aerosum shows jurky movements.
• Flagellar confugeration (9+2) exception Golenkinia (9+1), Chlamydomonas (9+0)
• Pseudocilia- Tetraspora
• Equal flagellation on anterior end, term isokontae.
• Pyrenoids are always associated with chloroplasts except in Microspora (Ulotrichales), Trentipohlia (Chetophorales)
• Isomorphic alternation of generation e.g. Ulva.
• CELL DIVISION
Phycoplast Phragmoplast
Always in algae Always in bryophytes and
Algae-Chara, Coleochate pulvinata
Zoospores are naked protoplasmic bodies which move by flagella or cilia
1. Biflagellate e.g. Ulothrix
2. Quadriflagellate – Ulothrix , Cladophora
3. Multiciliate - Oedogonium
Synzoospores – Multiciliate and multinucleate spores – Vaucheria
Aplanospores - non motile thin walled spore – Ulothrix , Chlorella
Hypnospores – thick walled, non motile spores during unfavorable condition –Ulothrix
XANTHOPHYCEAE
• In Xanthophyceae oogamy is rarely found e.g. Vaucheria
PHAEOPHYCEAE (Brown Algae)
• No unicellular forms in Phaeophyceae.
• Isomorphic alternation of generation is found in Ectocarpus.
• A male gamete with laterally inserted dimorphic flagella is found in Ectocarpus.
• Trichothallic growth is found in Ectocarpus
• Sargassum is commonly known as Gulf Weed
• The alga which exhibit gametic meiosis Sargassum.
• Sargassum has two laterally placed flagella in male gametes.
• Marine algae which is called Kelp – Laminaria.
• Sieve like cells are found in Laminaria
• Marine algae Laminaria is the chief source of alginate.
• Alginic acid derived from Brown algae (Laminaria).
• In Laminaria and Macrocystis alginic acid occurs in the middle lamellae and primary wall.
• Iodine is obtained from kelps (brown algae) e.g., Laminaria, Eisenia etc.
RHODOPHYCEAE (Red Algae)
• Rhodophyceae have one unicellular form – Porphyridium
• Alternation of generation in Polysiphonia is diplobiontic and triphasic.
• Red algae has a single thylakoid per granum
• Carpospores of Batrachospermum are: naked and nonmotile
• The site of reduction division in red algae- in Batrachospermum = carposporophyte, in Polysiphonia = tetrasporangia.
• Agar-agar is obtained from red algae such as Geledium, Gracillaria etc.
BRYOPHYTES
BRYOPHYTES
IMPORTANT POINTS TO REMEMBER
• Brophytes are the first land or terrestrial plants.
• Bryophytes are adapted to land by having a waxy coating on aerial parts.
• Plant body is gametophyte.
• Sex organs are multicellular and jacketed.
• Antherozoids are biflagellate and water is essential for fertilisation.
• Zygote does not divide meiotic ally but divides mitotic ally forming a multicellular embryo
• Sporophyte is usually differentiated into foot, seta and capsule except Riccia, Ricciocarpus where foot and seta are absent.
• Sporophyte remains dependent on gametophyte for its whole life.
• Spores are produced in the capsule by meiosis and all are of one kind, i.e., plants are homosporous.
• Most bryophytes are autotrophic but a few are saprophytic, e.g., Buxbaumia aphylla, Cryptothallus mirabilis
• Majority of the bryophytes are terrestrial and a few are aquatic, e.g. Riccia fluitans, Ricciocarpus natans, Fontmalis antipyretica and Riella sp.
• Some of the fossil bryophytes are : Hepaticites, Naiadita etc.
• Oldest fossil bryophyte Hepaticites was first described by WaIter (1925) from upper carboniferous period.
• The oldest bryophyte fossils are 350 million years old.
• Naiadia described by Harris is a bryophyte from Triassic of England.
• The smallest bryophyte is Zoopsis argentea belonging to order Acrogynous Jungermanniales (Hepaticae) and male thallus of Buxbaumia aphylla which measure only few mm.
• Dawsonia is the tallest bryophyte (40-50cm in height) and Fontinalis antipyretica is the longest bryophyte (50-70 cm in length)
• Bryophytes become seldom taller than 20 cm due to lack of vascular tissue.
• Smallest bryophyte is Zoopsis.
• Largest thalloid bryophyte is Monoclea forsteri which is 20 cm in length and 5 cm in width.
• Riccia (Hepaticae) was named in honour of a Florentine politician P. F. Ricci.
• The name Marchantia was given in honour of Nicolas Marchant, the director of botanical garden Gaston d’orleans, Bloir, France.
• Pellia was named in honour of Leo pol do Pelli-fabroni, a lawyer of Florence, Italy who was the friend of Raddi, the discoverer of Pellia.
• Funaria is called as common moss or green moss or cord moss.
• Sphagnum is also known as Peat moss, Turf moss or Bog moss.
• Polytrichum is commonly called Hairy cap moss.
• Pogonatum is commonly called Golden maiden-hair moss.
• Largest archegonium in plant kingdom is of Funaria.
• Gemmae in Funaria are formed at the tips of chloronemal branches of protonema.
• Apospory is present in Funaria. It introduces polyploidy in the race.
• Sphagnum upon death gets compressed and fossilised over thousands of years to produce a dark spongy mass called peat which is dried, cut and used as fuel as well as good manure.
• Dry Sphagnum can absorb 18-26 times its weight of water. In older times, Sphagnum moss was used in place of absorbent cotton.
• Polytrichum commune was employed in removing kidney stones.
• The air sacs in capsule of moss act as shock absorbers.
• Riccia is a cosmopolitan terrestrial liverwort having dichotomously branched pros¬trate thallus which bears two types (smooth walled and tuberculate) of unicellular unbranched rhizoids for anchorage and simple scales along the margin on ventral side and distinct furrow on dorsal side.
• Male sex organ is antheridium and female is archegonium, which are multicellular and jacketed.
• Sporophyte or sporogonium of Riccia is simplest consisting of capsule only and lacks elaters, foot and seta.
• Marchantia thalli bear cup-like structures called gemmae cups on mid-dorsal line. Gemma cup produces numerous, bilobed, vegetative reproductive bodies called gemmae.
• Marchantia thalli bear 2 types of scales (appendaged and simple) in 2-3 rows on ei¬ther sides of mid rib.
• In Marchantia antheridia and archegonia are found on special vertically stalked struc-tures the antheridiophores and archegoniophores respectively.
• Sporophyte of Marchantia is differentiated into foot, seta and capsule and capsule produces spores and elaters. Elaters are spindle-shaped having two spiral thicken¬ ings.
• Elaters in Marchantia are diploid and have spiral thickenings. They help in spore dispersal.
• Indicator of Cu rich substratum (Cuprophule)- Mielichhofera elongate, M. mielichhoferi, Merceya ligulata, Drypodon ( Cu mosses)
• Those plants in which apical cell is not involved in formation of archegonia are called anacrogynous.
• Cryptothallus is a saparophyte.
• The sex chromosome were discovered for the first time in plants – Sphaerocarpus
HEPATICAE
• In a fully mature sporophyte of Riccia the spore mass is enclosed in Ventre.
• There are 5 rows of neck canal cells in the archegonium of Porella.
• The protective device over the developing sporophyte is shoot calyptra in Frullania.
• Columella absent in Pellia epiphylla.
• Pellia is anacrogynous in nature.
• All jungermanniales contain oil bodies e.g. Frullania.
• Pellia shows in situ germination of spores.
ANTHOCEROTAE
• Endophytic algae are found in Anthoceros
• Which shows indeterminate growth of the sporophyte Anthoceros
• In Anthoceros the sporophyte is inderminate in growth.
• Link between algae and Pteridophyte - Anthoceros.
• The antheridial chamber containing a bunch of antheridia are found in Anthoceros.
• Anthoceros is characterized by the presence of single chloroplast in the gametophytic cells.
• The origin of sporogenous tissue is from amphithecium in Anthoceros.
• Which show the characteristic of green algae and as well as lower vascular plant – Anthoceros.
MUSCI
• The Calyptra of moss sporophyte is - haploid
• Peat moss – Sphagnum
• Retort cells are found in Sphagnum stem
• The seta is absent in the sporogonium of Sphagnum
• In Sphagnum the gametophyte structure compensating for the absence of seta is known as Pseudopodium.
• Pogonatum is endohydric in nature.
• Nematodontus peristome – Pogonatum
• Septate and branched rhizoids are found in Funaria.
SPOROGONIUM
Foot and seta absent Riccia
Foot is indistinguishable Pallavicinia
Seta is indistinct Sphagnum, Archidium
Shape of capsule Genera
Spherical Riccia, Pellia, Fossombronia, Metzgeria, Frullania, Sphaerocarpus and Sphagnum
Ovoid Riccardia, Treubia
Cylindrical Anthoceros, Pallavicinia radiculosa, Calobryam, Monoclea, Tetraphis pellucida
Oblong Haplomitrium, Brachythecium velutinium
Pyriform Funaria hygometrica
Inside the jacket of capsule
Spores only Riccia, Ricciocarpos
Spores + rounded or oval sterile nurse cells Sphaerocarpus, Geothallus, Riella, Carpos (Monocarpus) and Corsinia
Spores + Elaters
Elaters Spiral thickening
1 Macvicaria,Riccardia indica, Stephensoniella and genera belonging to Lejeuneaceae and Frullaniaceae
2 Marchantia , Pellia, Calycularia and Blasia
3 Athalamia pinguis, Sauchia and Mannia (Grimaldia)
• Elaters are either diffuse, and unattached to the wall of the capsule---- Targionia, Marchantia, Porella
• Elaters are attached to the wall of capsule----- in some Jungermanniales
• In some genera there is a coherent mass of sterile tissue known as elaterophore
• Basal Elaterophore – Pellia
• Apical Elaterophore – Riccardia, Makinoa, Metzgeria
Elaterophore occupy an axial position in the capsule and are attached at the apical (distal) end of the capsular cavity Makinoa, Riccardia and Metzgeria
At the basal end Pellia, Noterocladia,Calycularia crispula and Schistochila Splachnophylla
• Such mosses whose capsule open by irregular splitting and do not by the definite operculum or by any other regular method of dehiscence such as valves, slits etc. are known as cleistocarpous mosses e.g. Acaulon, Pleuridium, Phascum and Archidium.
• In stegocarpus mosses the distal region of the capsule, above the fertile portion , is specialized in relation to spore dispersal as the operculum and peristome. The operculum usually separates from the rest of the capsule by a regular horizontal fissure and the line of the separation is characteristically constructed. e.g. Tetraphis, Funaria, Dicranella, Barbula, Splachnum
• On the basis of origin and fundamental structure the peristome can be divided in to two main types, and these two types form the basis of two main divisions (clans) of Bryidae, Nematodonteae and Arthrodonteae, they have been called nematodontous and arthrodontous peristome repectively.
Peristome Characters
Nematodontous (a) the peristome forming zone consist of several concentric layers of the cells of amphithecium,
(b) the peristome teeth are solid consisting of bundle of whole dead cells , and are without articulations or external markings other than those caused by the outline of cells.
Arthrodontous (a) the peristome forming zone consist of either of two or three layers of cells of amphithecium,
(b) the peristome teeth are thin, membranous, transversely barred and articulated, and are not made up of cells but consist solely of plates representing the thickened portions of the walls of two or three concentric cell layers.
IMPORTANT POINTS TO REMEMBER
• Brophytes are the first land or terrestrial plants.
• Bryophytes are adapted to land by having a waxy coating on aerial parts.
• Plant body is gametophyte.
• Sex organs are multicellular and jacketed.
• Antherozoids are biflagellate and water is essential for fertilisation.
• Zygote does not divide meiotic ally but divides mitotic ally forming a multicellular embryo
• Sporophyte is usually differentiated into foot, seta and capsule except Riccia, Ricciocarpus where foot and seta are absent.
• Sporophyte remains dependent on gametophyte for its whole life.
• Spores are produced in the capsule by meiosis and all are of one kind, i.e., plants are homosporous.
• Most bryophytes are autotrophic but a few are saprophytic, e.g., Buxbaumia aphylla, Cryptothallus mirabilis
• Majority of the bryophytes are terrestrial and a few are aquatic, e.g. Riccia fluitans, Ricciocarpus natans, Fontmalis antipyretica and Riella sp.
• Some of the fossil bryophytes are : Hepaticites, Naiadita etc.
• Oldest fossil bryophyte Hepaticites was first described by WaIter (1925) from upper carboniferous period.
• The oldest bryophyte fossils are 350 million years old.
• Naiadia described by Harris is a bryophyte from Triassic of England.
• The smallest bryophyte is Zoopsis argentea belonging to order Acrogynous Jungermanniales (Hepaticae) and male thallus of Buxbaumia aphylla which measure only few mm.
• Dawsonia is the tallest bryophyte (40-50cm in height) and Fontinalis antipyretica is the longest bryophyte (50-70 cm in length)
• Bryophytes become seldom taller than 20 cm due to lack of vascular tissue.
• Smallest bryophyte is Zoopsis.
• Largest thalloid bryophyte is Monoclea forsteri which is 20 cm in length and 5 cm in width.
• Riccia (Hepaticae) was named in honour of a Florentine politician P. F. Ricci.
• The name Marchantia was given in honour of Nicolas Marchant, the director of botanical garden Gaston d’orleans, Bloir, France.
• Pellia was named in honour of Leo pol do Pelli-fabroni, a lawyer of Florence, Italy who was the friend of Raddi, the discoverer of Pellia.
• Funaria is called as common moss or green moss or cord moss.
• Sphagnum is also known as Peat moss, Turf moss or Bog moss.
• Polytrichum is commonly called Hairy cap moss.
• Pogonatum is commonly called Golden maiden-hair moss.
• Largest archegonium in plant kingdom is of Funaria.
• Gemmae in Funaria are formed at the tips of chloronemal branches of protonema.
• Apospory is present in Funaria. It introduces polyploidy in the race.
• Sphagnum upon death gets compressed and fossilised over thousands of years to produce a dark spongy mass called peat which is dried, cut and used as fuel as well as good manure.
• Dry Sphagnum can absorb 18-26 times its weight of water. In older times, Sphagnum moss was used in place of absorbent cotton.
• Polytrichum commune was employed in removing kidney stones.
• The air sacs in capsule of moss act as shock absorbers.
• Riccia is a cosmopolitan terrestrial liverwort having dichotomously branched pros¬trate thallus which bears two types (smooth walled and tuberculate) of unicellular unbranched rhizoids for anchorage and simple scales along the margin on ventral side and distinct furrow on dorsal side.
• Male sex organ is antheridium and female is archegonium, which are multicellular and jacketed.
• Sporophyte or sporogonium of Riccia is simplest consisting of capsule only and lacks elaters, foot and seta.
• Marchantia thalli bear cup-like structures called gemmae cups on mid-dorsal line. Gemma cup produces numerous, bilobed, vegetative reproductive bodies called gemmae.
• Marchantia thalli bear 2 types of scales (appendaged and simple) in 2-3 rows on ei¬ther sides of mid rib.
• In Marchantia antheridia and archegonia are found on special vertically stalked struc-tures the antheridiophores and archegoniophores respectively.
• Sporophyte of Marchantia is differentiated into foot, seta and capsule and capsule produces spores and elaters. Elaters are spindle-shaped having two spiral thicken¬ ings.
• Elaters in Marchantia are diploid and have spiral thickenings. They help in spore dispersal.
• Indicator of Cu rich substratum (Cuprophule)- Mielichhofera elongate, M. mielichhoferi, Merceya ligulata, Drypodon ( Cu mosses)
• Those plants in which apical cell is not involved in formation of archegonia are called anacrogynous.
• Cryptothallus is a saparophyte.
• The sex chromosome were discovered for the first time in plants – Sphaerocarpus
HEPATICAE
• In a fully mature sporophyte of Riccia the spore mass is enclosed in Ventre.
• There are 5 rows of neck canal cells in the archegonium of Porella.
• The protective device over the developing sporophyte is shoot calyptra in Frullania.
• Columella absent in Pellia epiphylla.
• Pellia is anacrogynous in nature.
• All jungermanniales contain oil bodies e.g. Frullania.
• Pellia shows in situ germination of spores.
ANTHOCEROTAE
• Endophytic algae are found in Anthoceros
• Which shows indeterminate growth of the sporophyte Anthoceros
• In Anthoceros the sporophyte is inderminate in growth.
• Link between algae and Pteridophyte - Anthoceros.
• The antheridial chamber containing a bunch of antheridia are found in Anthoceros.
• Anthoceros is characterized by the presence of single chloroplast in the gametophytic cells.
• The origin of sporogenous tissue is from amphithecium in Anthoceros.
• Which show the characteristic of green algae and as well as lower vascular plant – Anthoceros.
MUSCI
• The Calyptra of moss sporophyte is - haploid
• Peat moss – Sphagnum
• Retort cells are found in Sphagnum stem
• The seta is absent in the sporogonium of Sphagnum
• In Sphagnum the gametophyte structure compensating for the absence of seta is known as Pseudopodium.
• Pogonatum is endohydric in nature.
• Nematodontus peristome – Pogonatum
• Septate and branched rhizoids are found in Funaria.
SPOROGONIUM
Foot and seta absent Riccia
Foot is indistinguishable Pallavicinia
Seta is indistinct Sphagnum, Archidium
Shape of capsule Genera
Spherical Riccia, Pellia, Fossombronia, Metzgeria, Frullania, Sphaerocarpus and Sphagnum
Ovoid Riccardia, Treubia
Cylindrical Anthoceros, Pallavicinia radiculosa, Calobryam, Monoclea, Tetraphis pellucida
Oblong Haplomitrium, Brachythecium velutinium
Pyriform Funaria hygometrica
Inside the jacket of capsule
Spores only Riccia, Ricciocarpos
Spores + rounded or oval sterile nurse cells Sphaerocarpus, Geothallus, Riella, Carpos (Monocarpus) and Corsinia
Spores + Elaters
Elaters Spiral thickening
1 Macvicaria,Riccardia indica, Stephensoniella and genera belonging to Lejeuneaceae and Frullaniaceae
2 Marchantia , Pellia, Calycularia and Blasia
3 Athalamia pinguis, Sauchia and Mannia (Grimaldia)
• Elaters are either diffuse, and unattached to the wall of the capsule---- Targionia, Marchantia, Porella
• Elaters are attached to the wall of capsule----- in some Jungermanniales
• In some genera there is a coherent mass of sterile tissue known as elaterophore
• Basal Elaterophore – Pellia
• Apical Elaterophore – Riccardia, Makinoa, Metzgeria
Elaterophore occupy an axial position in the capsule and are attached at the apical (distal) end of the capsular cavity Makinoa, Riccardia and Metzgeria
At the basal end Pellia, Noterocladia,Calycularia crispula and Schistochila Splachnophylla
• Such mosses whose capsule open by irregular splitting and do not by the definite operculum or by any other regular method of dehiscence such as valves, slits etc. are known as cleistocarpous mosses e.g. Acaulon, Pleuridium, Phascum and Archidium.
• In stegocarpus mosses the distal region of the capsule, above the fertile portion , is specialized in relation to spore dispersal as the operculum and peristome. The operculum usually separates from the rest of the capsule by a regular horizontal fissure and the line of the separation is characteristically constructed. e.g. Tetraphis, Funaria, Dicranella, Barbula, Splachnum
• On the basis of origin and fundamental structure the peristome can be divided in to two main types, and these two types form the basis of two main divisions (clans) of Bryidae, Nematodonteae and Arthrodonteae, they have been called nematodontous and arthrodontous peristome repectively.
Peristome Characters
Nematodontous (a) the peristome forming zone consist of several concentric layers of the cells of amphithecium,
(b) the peristome teeth are solid consisting of bundle of whole dead cells , and are without articulations or external markings other than those caused by the outline of cells.
Arthrodontous (a) the peristome forming zone consist of either of two or three layers of cells of amphithecium,
(b) the peristome teeth are thin, membranous, transversely barred and articulated, and are not made up of cells but consist solely of plates representing the thickened portions of the walls of two or three concentric cell layers.
PTERIDOPHYTES
PTERIDOPHYTES
IMOPORTANT POINTS TO REMEMBER
• Pteridophytes ( pteron = feather, phyton = plant i.e. plants with feather like leaves) are cryptogams with well developed vascular system also known as vascular cryptogams.
• Term ‘pteridophyte’ is given by E. Haeckel for plants with feather like fronds. First group of tracheophytes. Plant body is sporophytic (2n).
• Also known as vascular cryptogams, vascular amphibians, snake of the plant kingdom, seedless tracheophytes.
• Origin- 400 millions years ago in Silurian period of the Palaeozoic era.
• Pteridophytes were dominated in- Devonian period.
• They are the most prmitive living and fossil vascular plants.
• According to available fossil records the (Psilophytes are the first land vascular plants (i.e., most primitive vascular plants).
• Psilotales like Rhynia were first tracheophytes.
• Most primitive vascular land plants are Psilophytales members, e.g., Rhynia, Horneophyton (Hornea), Cook¬sonia, Asteroxylon and Psilophyton, etc. Pteridophytes have a long fossil history. They formed the dominant flora of the carboniferous period of palaeozoic era, when tree-like forms were common. Most part of coal is derived from these pteridophytes.
• Rhynia was described by Kidston and Lang from the Devonian period.
• Rhynia is a fossil pteridophyte (of lower devonian period of palaeozoic era), which is rootless and leafless and was discovered by Kidson and Lang (1913) from Rhynichert beds, Aberdeenshire, Scotland.
• According to the fossil records, Cooksonia (of late silurian period of palaeozoic era, about 400 milIion years old) is the oldest known vascular plant.
• Psilophyton is the first fossil member discovered by Sir William Dawson (1858).
• The ‘telome theory’ for the origin of pteridophytes was proposed by Zimmermann (1952). The telome is the extreme portion of the plant body from the tip to the next point of branching. Telome theory explains elaboration of simplest sporophyte (like Rhynia) into modern, complex sporophyte. Telome is ultimate terminal part of a dichotomous axis that has given rise to all parts of land plants.
• They are usually terrestrial and some are aquatic, e.g., Marsilea, Azolla, Salvinia, Regnellidium, Pilularia etc.
• The species of Lycopodium epiphytic in nature – L. phlegmaria.
• Azolla and Salvinia are free-floating while Marsilea, Regnellidium and Pilularia are amphibious. These are the water ferns.
• Azolla leaves enclose symbiotic blue green alga Anabaena azollae.
• Azolla has become important in agriculture because it is being used as a – Biofertilizer
• Annuals- Azolla, Salvinia
• Pernnials- Angiopteris , Osmunda
• Aquatic- Azolla, Isoetes, Marsilea, Salvinia
• Xerophytic- Selaginella rupestris, S. lepidophylla, S. densa, Equisetum arvense
• Woody ferns- Angiopteris, Marattia
• Smallest pteriophyte = Azolla (an aquatic fern) Largest pteriophyte = Cyathea (tree fern)
• Common names.
o Club moss- Lycopodium (Creeping pine, Trailing pine)
o Quill worts- Isoetes
o Spike moss or little club moss- Selaginella
o Bird's nest moss- Selaginella rupestris
o Giant Horsetails- Calamites
o Horse tail- Equisetem
o Adder’s tongue fern- Ophioglossum
o Royal fern- Osmunda
o Bracken Fern- Pteridium
o Maiden hair fern or Waking fern- Adiantum
o Polypody- Polypodium
o Sword fern- Nephrolepis
o Water fern- Marsilea
o Mosquito fern- Azolla
• Lycopodium commonly called club moss, is homosporopus and eligulate pteridophyte.
• Plant body is sporophyte and differentiated into root, stem and leaves.
• The brown coloured outgrowth existing over the petile and rhizome of fern is known as Ramenta.
• Vascular tissues are present. Xylem usually lacks vessels and phloem lacks companion cells.
• Primary roots are ephemeral and are soon replaced by adventious roots. The root has a permanent growing apex.
• Stem also have a permanent growing apex.
• In pteridophytes branches do not arise from the axil of leaves as in spermophytes.
• In Selaginella, Marilea, Isoetes, Pteridium, Regnellidium, Pilularia vessels may be present.
• Pteridophyte which shows chloroplast having pyrinoids – Selaginella
• Vascular tissues are present. They are of two types, xylem and phloem. In xylem, true vessels are absent. In phloem, companion cells are absent and sieve cells are present.
• Stelar theory in Pteridophytes was established by Van Tieghem and Douliot (1886).
• Types of stele:
o Haplostele: e.g., Rhynia
o Actinostele: e.g., Lycopodium serratum
o Plectostele: e.g., Lycopodium clavatum
o Dictyostele : e.g., Dryopteris, Adiantum etc.
• The only pteridophyte which has laticiferous elements in the stem is Regnellidium diphyllum.
• Usually the xylem of fern is made up of only tracheids.
• Pteridophytes lacking leaf gaps – Microphyllous pteridophytes with univered leaves lack leaf gap in stem stele of Equisetum, Selaginella, Lycopodium.
• The living example resembling a telome is exhibited by Psilotum.
• In Equisetum stem, the cavity formed by dissolution of protoxylem is known as Carinal canal.
• Valicular and carinal canal are found in – Equisetum
• Mature plant body is independent sporophyte which is differentiated into true roots, stem and leaves. Stem and roots of Lycopodium clavatum show plectostele.
• In Adiantum caudatum and a few other species, adventitious buds develop at leaf tips. When such leaf tips happen to touch the soil, they form new plants. The process helps in spreading the fern over a large area. Because of this reason Adiantum caudatum is also called walking fern and maiden hair fern.
• Adiantum - Maiden hair fern (because of shining, smooth and blackish hair-like petioles.)
• Sellaginella commonly called ‘spike moss’ is ligulate and heterosporous pteridophyte. Plants of some species such as Selaginella lepidophylla, S. pilifera are sold as curiosi-ties under the name of ‘resurrection plants’.
• Several species of Lycopodium often used Chrismas wreaths and other decora¬tions hence they are commonly called ‘Christmas green’.
• Spores of Lycopodium are used as dusting powder due to water repellent and also used in the manufacture of fireworks of lightening due to being highly inflammable.
• Stems of Selaginella usually possess trabeculed endodermis.
• Asexual spores are produced inside sporangia by meiosis.
• Sporangia are usually borne on or in the axil of leaves called sporophylls. e.g. Lycopodium, Selaginella, Pteris, Nephrolepis, Adiantum etc. In some plants sporangia are produced within specialized structures called sporocarps, e.g. Marsilea, Salvinia, Azolla, Regnellidium, Pilularia etc.
• Meiospores are formed inside sporangia. Sporangia are associated with leaves called sporophylls. Sporangium development is of two types:
o Leptosporangiate - When sporangia develops from single superficial cell. e.g. Pteris, Dryopteris, Adiantum.
o (ii) Eusporangiate - from group of cells. e.g. Selaginella, Equisetum.
• Spores are usually all alike (i.e Homosporous) e.g., Lycopodium, Pteris, Adiantum, Pteridium etc. or they are of two different sizes (i.e., Heterosporous) e.g., Selaginella, Isoetes, Marsilea, Azolla, Salvinia etc.
• Heterosporus fern is Marsilea.
• In Adiantum. the sori are borne submarginal1y at the distal end on the under surface of the leaflets. The margin of the leaflet is reflexed to cover the sorus. The reflexed margin is known as false indusium.
• Spores on germination form gametophytes or prothalli as independent plants.
• Zygote develops into sporophyte which remains dependent on gametophyte only during its early stages and later on becomes an independent plant.
• Origin of seed habit is indicated by Pteridophytes like Selaginella, Isoetes etc.
• Marsilea, Azolla, Salvinia, Regnellidium, Pilularia are heterosporous aquatic ferns, whose spore producing structures are called sporocarps. The rhizome of Marsilea shows amphiphloic siphonostele.
• Spores of Equisetum contain chloroplasts (also of Funaria), and each spore is surrounded by four layered wall. The outermost layer is called epispore which splits into two narrow, ribbon-shaped bands called elaters. These elaters are hygroscopic and help in the dispersal of spores.
• Spores of Lycopodium after germination develop independent gametophytes called prothalli which usually possess endophytic mycorrhiza.
• Antherozoids of Lycopodium and Selaginella are biflagellate like bryophytes.
• In Selaginella male gametes are biflagellate.
• Hydroscopic spoon shaped elaters are found on the spores of - Equisetum
• Sex organs are multicellular and jacketed, antheridia are reduced. Archegonia are partially embedded. Archegonial neck is 4-rowed.
• Sperms are flagellate. They require an external supply of water for swimming to reach archegonia.
• The mucilage oozing out of neck of archegonium in Selaginella and fern contains malic acid. The neck canal of archegonium in Selaginella and fern contains only one neck canal cell.
• Embryo stage is present. Embryogeny is of two types:
o Exoscopic embryogeny: Axis of embryo is directed towards archegonial neck e.g. Equisetum
o (ii) Endoscopic: Axis of embryo is directed inward towards venter e.g. Selaginella.
• Development of embryo: .
o Holoblastic -When entire zygote is involved in embryonic development. e.g. Ferns.
o Meroblastic- When part of zygote is involved in embryonic development e.g. Selaginella.
• Heteromorphic or heterologous alternation of generations is present in the life cycle.
• SPOROPHYTE (2n)→R/D→ spores(n)→GAMETOPHYTE (n)
• Apospory: It is development of diploid gametophyte from sporophyte without meiosis. It was reported by Druery in Athyrium. Due to apospory, polyploidy common in fern.
• SPOROPHYTE (2n)→ APOSPORY→GAMETOPHYTE (2n)
• Apogamy : It is development of haploid sporophyte from gametophyte without fertilisation. It was reported by Farlow in Pteris cretica.
• GAMETOPHYTE (n) →APOGAMY→ SPOROPHYTE(n)
• Highest number of chromosomes in plants has been reported in a pteridophyte, Ophioglossum, where 2n = 1262.
IMOPORTANT POINTS TO REMEMBER
• Pteridophytes ( pteron = feather, phyton = plant i.e. plants with feather like leaves) are cryptogams with well developed vascular system also known as vascular cryptogams.
• Term ‘pteridophyte’ is given by E. Haeckel for plants with feather like fronds. First group of tracheophytes. Plant body is sporophytic (2n).
• Also known as vascular cryptogams, vascular amphibians, snake of the plant kingdom, seedless tracheophytes.
• Origin- 400 millions years ago in Silurian period of the Palaeozoic era.
• Pteridophytes were dominated in- Devonian period.
• They are the most prmitive living and fossil vascular plants.
• According to available fossil records the (Psilophytes are the first land vascular plants (i.e., most primitive vascular plants).
• Psilotales like Rhynia were first tracheophytes.
• Most primitive vascular land plants are Psilophytales members, e.g., Rhynia, Horneophyton (Hornea), Cook¬sonia, Asteroxylon and Psilophyton, etc. Pteridophytes have a long fossil history. They formed the dominant flora of the carboniferous period of palaeozoic era, when tree-like forms were common. Most part of coal is derived from these pteridophytes.
• Rhynia was described by Kidston and Lang from the Devonian period.
• Rhynia is a fossil pteridophyte (of lower devonian period of palaeozoic era), which is rootless and leafless and was discovered by Kidson and Lang (1913) from Rhynichert beds, Aberdeenshire, Scotland.
• According to the fossil records, Cooksonia (of late silurian period of palaeozoic era, about 400 milIion years old) is the oldest known vascular plant.
• Psilophyton is the first fossil member discovered by Sir William Dawson (1858).
• The ‘telome theory’ for the origin of pteridophytes was proposed by Zimmermann (1952). The telome is the extreme portion of the plant body from the tip to the next point of branching. Telome theory explains elaboration of simplest sporophyte (like Rhynia) into modern, complex sporophyte. Telome is ultimate terminal part of a dichotomous axis that has given rise to all parts of land plants.
• They are usually terrestrial and some are aquatic, e.g., Marsilea, Azolla, Salvinia, Regnellidium, Pilularia etc.
• The species of Lycopodium epiphytic in nature – L. phlegmaria.
• Azolla and Salvinia are free-floating while Marsilea, Regnellidium and Pilularia are amphibious. These are the water ferns.
• Azolla leaves enclose symbiotic blue green alga Anabaena azollae.
• Azolla has become important in agriculture because it is being used as a – Biofertilizer
• Annuals- Azolla, Salvinia
• Pernnials- Angiopteris , Osmunda
• Aquatic- Azolla, Isoetes, Marsilea, Salvinia
• Xerophytic- Selaginella rupestris, S. lepidophylla, S. densa, Equisetum arvense
• Woody ferns- Angiopteris, Marattia
• Smallest pteriophyte = Azolla (an aquatic fern) Largest pteriophyte = Cyathea (tree fern)
• Common names.
o Club moss- Lycopodium (Creeping pine, Trailing pine)
o Quill worts- Isoetes
o Spike moss or little club moss- Selaginella
o Bird's nest moss- Selaginella rupestris
o Giant Horsetails- Calamites
o Horse tail- Equisetem
o Adder’s tongue fern- Ophioglossum
o Royal fern- Osmunda
o Bracken Fern- Pteridium
o Maiden hair fern or Waking fern- Adiantum
o Polypody- Polypodium
o Sword fern- Nephrolepis
o Water fern- Marsilea
o Mosquito fern- Azolla
• Lycopodium commonly called club moss, is homosporopus and eligulate pteridophyte.
• Plant body is sporophyte and differentiated into root, stem and leaves.
• The brown coloured outgrowth existing over the petile and rhizome of fern is known as Ramenta.
• Vascular tissues are present. Xylem usually lacks vessels and phloem lacks companion cells.
• Primary roots are ephemeral and are soon replaced by adventious roots. The root has a permanent growing apex.
• Stem also have a permanent growing apex.
• In pteridophytes branches do not arise from the axil of leaves as in spermophytes.
• In Selaginella, Marilea, Isoetes, Pteridium, Regnellidium, Pilularia vessels may be present.
• Pteridophyte which shows chloroplast having pyrinoids – Selaginella
• Vascular tissues are present. They are of two types, xylem and phloem. In xylem, true vessels are absent. In phloem, companion cells are absent and sieve cells are present.
• Stelar theory in Pteridophytes was established by Van Tieghem and Douliot (1886).
• Types of stele:
o Haplostele: e.g., Rhynia
o Actinostele: e.g., Lycopodium serratum
o Plectostele: e.g., Lycopodium clavatum
o Dictyostele : e.g., Dryopteris, Adiantum etc.
• The only pteridophyte which has laticiferous elements in the stem is Regnellidium diphyllum.
• Usually the xylem of fern is made up of only tracheids.
• Pteridophytes lacking leaf gaps – Microphyllous pteridophytes with univered leaves lack leaf gap in stem stele of Equisetum, Selaginella, Lycopodium.
• The living example resembling a telome is exhibited by Psilotum.
• In Equisetum stem, the cavity formed by dissolution of protoxylem is known as Carinal canal.
• Valicular and carinal canal are found in – Equisetum
• Mature plant body is independent sporophyte which is differentiated into true roots, stem and leaves. Stem and roots of Lycopodium clavatum show plectostele.
• In Adiantum caudatum and a few other species, adventitious buds develop at leaf tips. When such leaf tips happen to touch the soil, they form new plants. The process helps in spreading the fern over a large area. Because of this reason Adiantum caudatum is also called walking fern and maiden hair fern.
• Adiantum - Maiden hair fern (because of shining, smooth and blackish hair-like petioles.)
• Sellaginella commonly called ‘spike moss’ is ligulate and heterosporous pteridophyte. Plants of some species such as Selaginella lepidophylla, S. pilifera are sold as curiosi-ties under the name of ‘resurrection plants’.
• Several species of Lycopodium often used Chrismas wreaths and other decora¬tions hence they are commonly called ‘Christmas green’.
• Spores of Lycopodium are used as dusting powder due to water repellent and also used in the manufacture of fireworks of lightening due to being highly inflammable.
• Stems of Selaginella usually possess trabeculed endodermis.
• Asexual spores are produced inside sporangia by meiosis.
• Sporangia are usually borne on or in the axil of leaves called sporophylls. e.g. Lycopodium, Selaginella, Pteris, Nephrolepis, Adiantum etc. In some plants sporangia are produced within specialized structures called sporocarps, e.g. Marsilea, Salvinia, Azolla, Regnellidium, Pilularia etc.
• Meiospores are formed inside sporangia. Sporangia are associated with leaves called sporophylls. Sporangium development is of two types:
o Leptosporangiate - When sporangia develops from single superficial cell. e.g. Pteris, Dryopteris, Adiantum.
o (ii) Eusporangiate - from group of cells. e.g. Selaginella, Equisetum.
• Spores are usually all alike (i.e Homosporous) e.g., Lycopodium, Pteris, Adiantum, Pteridium etc. or they are of two different sizes (i.e., Heterosporous) e.g., Selaginella, Isoetes, Marsilea, Azolla, Salvinia etc.
• Heterosporus fern is Marsilea.
• In Adiantum. the sori are borne submarginal1y at the distal end on the under surface of the leaflets. The margin of the leaflet is reflexed to cover the sorus. The reflexed margin is known as false indusium.
• Spores on germination form gametophytes or prothalli as independent plants.
• Zygote develops into sporophyte which remains dependent on gametophyte only during its early stages and later on becomes an independent plant.
• Origin of seed habit is indicated by Pteridophytes like Selaginella, Isoetes etc.
• Marsilea, Azolla, Salvinia, Regnellidium, Pilularia are heterosporous aquatic ferns, whose spore producing structures are called sporocarps. The rhizome of Marsilea shows amphiphloic siphonostele.
• Spores of Equisetum contain chloroplasts (also of Funaria), and each spore is surrounded by four layered wall. The outermost layer is called epispore which splits into two narrow, ribbon-shaped bands called elaters. These elaters are hygroscopic and help in the dispersal of spores.
• Spores of Lycopodium after germination develop independent gametophytes called prothalli which usually possess endophytic mycorrhiza.
• Antherozoids of Lycopodium and Selaginella are biflagellate like bryophytes.
• In Selaginella male gametes are biflagellate.
• Hydroscopic spoon shaped elaters are found on the spores of - Equisetum
• Sex organs are multicellular and jacketed, antheridia are reduced. Archegonia are partially embedded. Archegonial neck is 4-rowed.
• Sperms are flagellate. They require an external supply of water for swimming to reach archegonia.
• The mucilage oozing out of neck of archegonium in Selaginella and fern contains malic acid. The neck canal of archegonium in Selaginella and fern contains only one neck canal cell.
• Embryo stage is present. Embryogeny is of two types:
o Exoscopic embryogeny: Axis of embryo is directed towards archegonial neck e.g. Equisetum
o (ii) Endoscopic: Axis of embryo is directed inward towards venter e.g. Selaginella.
• Development of embryo: .
o Holoblastic -When entire zygote is involved in embryonic development. e.g. Ferns.
o Meroblastic- When part of zygote is involved in embryonic development e.g. Selaginella.
• Heteromorphic or heterologous alternation of generations is present in the life cycle.
• SPOROPHYTE (2n)→R/D→ spores(n)→GAMETOPHYTE (n)
• Apospory: It is development of diploid gametophyte from sporophyte without meiosis. It was reported by Druery in Athyrium. Due to apospory, polyploidy common in fern.
• SPOROPHYTE (2n)→ APOSPORY→GAMETOPHYTE (2n)
• Apogamy : It is development of haploid sporophyte from gametophyte without fertilisation. It was reported by Farlow in Pteris cretica.
• GAMETOPHYTE (n) →APOGAMY→ SPOROPHYTE(n)
• Highest number of chromosomes in plants has been reported in a pteridophyte, Ophioglossum, where 2n = 1262.
GYMNOSPERMS
GYMNOSPERMS
IMPORTANT POINTS TO REMEMBER
• Gymnosperms are the most primitive seed plants.
• Age of higher gymnosperms is mesozoic era. (Although origin of order Cycadofilicales (seed ferns) of gymnospeems is in late palaeozoic).
• Gymnosperms act as a connecting link (bridge) between pteridophytes and angiosperms.
• The Gymosperms flourished in the period following the Coal age. But nowadays, there are only four living orders- Cycadales, Ginkgoales, Coniferales and Gnetales. Out of these conifers are the most successful order of the gymnosperm. At one time, it is believed, vast areas of the earth's crust were covered with forests of conifers. Conifers are among the largest, heaviest and longest-lived organism of the world.
• Conifers do not shed there leaves like deciduous trees. Therefore, these remain green throughout the year (evergreen) and carry on photosynthesis even in the short days. Their evergreen habit is probably the reason for their success in the cold zones on the north.
• All gymnosperms are perennial woody plants forming either bushes or trees. Some of these are very large and live for thousand of years. e.g. Sequoia sempervirens
• All gymnosperms are perennials. They are trees or shrubs, mostly evergreen with needle-like leaves. None of the gymnosperms are herbs or annuals.
• Araucaria, a tall conifer from South America, grows well at lower altitudes and warmer climates.
• The term gymnospenn was used by Theophrastus It is smallest group in plantae with 70 genus and 900 living species. In India, 14 genus and 54 species are found.
• Roots of some gymnosperms have symbiotic relations with algae (e.g. coralloid roots of Cycas) or fungi (e.g. mycorrhizae in Pinus)
• Stem of Cycas is unbranched and in Zamia it is tuberous.
• Plants are predominantly woody, wood may be pycnoxylic (i.e., compact and hard) e.g. Pinus and other genera or it may be manoxylic (i.e. loose and soft) e.g. Cycas.
• Xylem lacks vessels (i.e. wood is nonporous) and phloem lacks companion cells. However in some plants vessels are present e.g. Gnetum, Ephedra, Welwitschia etc.
• Wood of Conifers is of great commercial importance. A good quantity of timber obtained from the species of Pinus, Cedrus, Abies etc. is used for making building arti-cles, furniture, railway sleepers, carriages etc.
• The wood of Juniperns virginiana is used for making pencils of high quality and its oil, called Red Cedar Wood oil, is used for clearing microscopic sections and for oil immersion lenses.
• All gymnosperms are perennial woody plants forming either bushes or trees. Some of these are very large and live for thousands of years. e.g. Sequoia sempervirens
• The term 'gymnosperm' was used by Theophrastus in his book "Enquiry into Plants".
• It is smallest group of plantae with 70 genus and 900 living species. In India 14 genus and 54 species are found.
• Leaves are generally dimoprphic, foliage and scale leaves.
• Foliage leaves do not have lateral veins. Transfusion tissue (hydrostereom) occurs internally for lateral transport.
• In some gymnosperms e.g. Ephedra, only scaly leaves are present.
• Wood is homoxylous but Gnetales bear vessels in xylem e.g. Ephedra, Gnetum, Welwitschia.
• Types of wood:
(i) Manoxylic: Soft wood, vascular tissues with medullary rays, commercially less important e.g. Cycas.
(ii) Pycnoxylic: Compact wood without or with narrow medullary rays, commerciallly more important e.g. Pinus.
(iii) Monoxylic: with single persistant cambium rings and bundles e.g. Pinus.
(iv) Polyxylic: With many persistant cambium rings and bundles e.g. Cycas.
• Conifers are the main sources of various types of resins which are insoluble in water but soluble in some organic solvents. Resins are used in the manufacture of varnishes, paints, medicines etc.
• Alkaloid ephedrine obtained from the species of Ephedra is used to cure cough, bronchitis, asthma etc.
• In some gymnosperms e.g. Ephedra foliata, Ephedra intermedia, bisporangiate cones can be seen.
• Male cones of gymnosperms are usually short lived.
• In Gnetales the ovules are bitegmic.
• Male gametes of Cycas and Ginkgo are motile.
• The embryo is endoscopic and there is tendency of polyembryony.
• In gymnosperms flowers are absent.
• Living fossils – Cycas, Ginkgo
• The endosperm in gymnosperms is haploid.
• Pollination is anemophilous .i.e. by wind
• Endosperm develops before fertilisation and is haploid.
• Polyebryony is of common occurrence.
• Characters common in fern and Cycas – circinate vernation and compound leaves.
• The largest size of male gamete is found in Cycas.
• Diploxylic vascular bundles are found in Cycas.
• The tissue between the pollen chamber and archegonial chamber of Cycas is neck canal cells.
• The microsporangia in Cycas microsporophylls are present on abaxial (lower) surface
• The position of microsporangia on the microsporophyll of Pinus is abaxial.
• If you are asked how many fruits are produced by single cone of Pinus. Answer is None
• Pinus – Pycnoxylic
• Nonporous wood – Pinus
• Polycotyledonous embryos are found in Pinus.
• Constituent of phloem of Pinus – sieve tubes and phloem parenchyma only.
• Gymnosperm said to have double fertilization- Ephedra.
• Gnetum shows the complete absence of archegonia in their ovule.
• Female gametophyte is tetrasporic in origin in Gnetum and Welwitschia.
• The syndetochelic stomata differs from haplochelic stomata in respect to their morphology and ontogeny.
• Podocarpus is regarded as living cordate
• Beck proposed the creation of group Progymnosperms
• Smallest gynmosperm = Zamia
• Largest gynmosperm = Sequoiadendron
• The three generations in seed are : (i) Testa. tegmen and perisperm represent parental sporophyte. ii) Endosperm represents female gametophyte ; (iii) Plumule, radicle, suspensor and cotyledons (embryo) represent future sporophyte.
• Polyembryony: It is the formation of more than one embryo inside a single seed. It was reported by Leewenhoek in oranges. Simple polyembryony is due to fertilisation of many eggs e.g. Pinus ovule has 2-8 archegonia. Cleavage polyembryony is true polyembryony and very common. It is due to splitting of embryo tissue. Adventive polyembryony is the formation of extra embryos directly from diploid cells (e.g.. rosette cells) other than embryonal cells.
• Drug ephedrine is obtained from Ephedra which is used in curing respiratory ailments including asthma.
• Ginkgo biloba is known as ‘maiden hair tree’ and ‘Pagoda tree’ and produce ciliated sperms.
ECONOMIC IMPORTANCE OF GYMNOSPERMS
Gymnosperms are economically very important. The mem¬bers of this group are variously used by human beings as food, as medicines, as plants for decoration and in industries.
Economic importance of cycadophytae
1. Ornamental value
They look like palm tree and are evergreen in nature. Foliage leaves of some species, i.e., C. revlluta, C. circinalis, C. rumphii and C. beddomei are used for decoration purposes as they remain fresh for long period.
2. Food value
Different parts of the Cycas plants are used as food material.
(i) Stem portion of C. revoluta and C. circinalis is a good source of ‘Sago’, a kind of starch used in making bread by poor people.
(ii) Pith of the plant Encephlartos is used in the preparation of Kaffer bread.
(iii) Seeds and seed kernels of some species of Cycas are roasted and taken as food.
(iv) Leaves: Young succulent leaves of some species of Cycas are cooked as vegetable.
(v) Seeds and stem of Cycas revoluta are used in making wine in Japan.
(vi) Zamia is rich in starch and is used as food by many Indians.
3. Medicinal value
Many useful medicines are prepared and extracted from the different parts of the Cycas plants.
(i) Leaves: The leaves of C. circinalis are medicinally very important. The fresh juice extracted from the leaves is used as medicine in stomach disorders, blood vomiting and other skin diseases.
(ii) Seeds and megasporophylls: Seeds and crushed bark of Cycas and its megasporophylls when mixed with coconut oil are used as poultice for sores and wounds in South India.
(iii) Pollen grains of some Cycas plants are reported to have some narcotic effect.
Economic importance of coniferophytae
The many useful products come from conifers. Papers and other products, such as the lumber used to build homes, come from conifers. Conifers are also used to make the rayon fibres in clothes, cellophane food wrappers and turpentine.
1. Ornamental value
Almost all the members are of ornamental value. Ginkgo biloba is often named as ‘Maiden Hair Tree’ because of its beautiful leaves. Thuja, Araucaria, Abies, Cryptomeria, Pinus, Taxus are grown in parks.
2. Edible value
(i) Seeds: Seeds of some species are edible, e.g., Pinus gerardiana (chilgoza), P. edulis, P. pinea. Seeds of Gnetum gnemon are also edible. Seeds of Ginkgo biloba are nutritious.
(ii) Shoots: Shoots and inflorescence of Gnetum sps are widely used as vegetables in many countries.
3. Medicinal value
(i) Gnetum ula is a common source of edible oil. It is also used as massage in rheumatic pain. A volatile oil extracted from the shoots and leaves of Thuja is used as vermifuge. Oil of Juniperus species is medici¬nally important.
(ii) Leaves: Leaves and seeds of Taxus are used as medi¬cines.
(iii) A medicine of cancer called ‘Taxol’ is obtained from the bark of Taxus.
(iv) An important alkaloid ‘ephedrine’ is obtained from Ephedra, used in treatment of asthma, cough, cold and other respiratory disorders.
4. Industrial use
Wood: Some of the important conifers like spruce or Picea (maximum cellulose content) are an important source of pulp wood and are used in manufacture of paper P. markussii is a valuable source of raw material. Timber is also obtained from various conifers. Pinus (chir), Abies (fir), Cedrus (cedar and deodar), Sequoia (red wood) are the chief source of various types of wood. The wood of Juniperus is used in making pencils, scales and holders. The wood of Biota (Thuja) is soft, brittle and durable. Woods of many conifers is used in the manufacture of paper. eg. Pinus. Conifers are the source of soft wood for construction, packing and plywood industry eg. Cedrus, Agathis
Turpentine is obtained from the resin of Pinus. It is used as solvent in paint and polishes. It is also used medicinally for pain, bronchitis etc. Saw dust of conifers is used in making linoleum and plastics. Pinus species yield a resin called rosin which is used in water proofing and sealing joints.
CLASSIFICATION OF GYMNOSPERMS
Chamberlain (1934) has classified gymnosperms into two classes 1. class Cycadophyta 2. Class Coniferophyta .
I. Cycadophytae
Divided into 3 orders:
1. Cycadofilicales or Pteridospermales or Pteridosperms (Seed ferns)
These are fossils. They show some characters of ferns and some of gymnosperms. Their origin is in late palaeozoic. These are the connecting link between pteridophytes and gymnosperms, e.g., Medullosa and Lyginopteris.
2. Bennettitales or Cycadaeodales or fossil cycads- Their leaf bases are permanently attached to stem, e.g. Williamsonia and Williamsoniella.
3. Cycadales or Living cycads- They have typical palm-like appearance. Stem is un¬branched, leaves large and male gametes are ciliated, wood is manoxylic, e.g. Cycas, MicroCycas, Zamia, Stangeria, etc. Zamia pygmaea is the smallest gymnosperm (25 cm in height).
II. Coniferophytae
The class Cycadophyta consists of plants with simple stem, thick cortex but thin wood and simple sporophylls. The class Coniferophyta consists of plants with profusely branched stem, thin cortex, thick wood and complex sporophylls. Divided into 4 orders:
1. Cordaitales- Fossils, e.g., Cordaites and Poroxylon.
2. Ginkgoales- Many fossils and a single living genus, i. e., Ginkgo biloba. which is commonly known as ‘Maiden Hair Tree’ (because of the resemblance of its leaves with those of ‘Maiden Hair Fern’ or Adiantum). It is also called ‘Living fossil’ (because single living genus in a big fossilized order). Kaemfer (1690) studied this maiden hair tree and named it as Ginkgo.
3. Coniferales
It is the largest order of modem gymnosperms. Here wood is pycnoxylic, stem branched, foliage leaves simple and reduced, called needles, e.g.. Pinus (pine), Podocarpus. Thuja (Biota), Sequoia (red wood tree), Araucaria (Christmas tree or Monkey's puzzle), Cupressus, Picea (spruce), etc. Sequoia is the largest gymnosperm (366 ft in height).
4. Gnetales
It is the highest order of gymnosperms and is a connect¬ing link between gymnosperms and angiosperms. This order is peculiar as it has 3 genera, which are quite different from each other.
e.g., Gnetum, Ephedra (Jointed fir) and Welwitschia. This is the only order in gymnosperms where vessels are present in xylem.
IMPORTANT POINTS TO REMEMBER
• Gymnosperms are the most primitive seed plants.
• Age of higher gymnosperms is mesozoic era. (Although origin of order Cycadofilicales (seed ferns) of gymnospeems is in late palaeozoic).
• Gymnosperms act as a connecting link (bridge) between pteridophytes and angiosperms.
• The Gymosperms flourished in the period following the Coal age. But nowadays, there are only four living orders- Cycadales, Ginkgoales, Coniferales and Gnetales. Out of these conifers are the most successful order of the gymnosperm. At one time, it is believed, vast areas of the earth's crust were covered with forests of conifers. Conifers are among the largest, heaviest and longest-lived organism of the world.
• Conifers do not shed there leaves like deciduous trees. Therefore, these remain green throughout the year (evergreen) and carry on photosynthesis even in the short days. Their evergreen habit is probably the reason for their success in the cold zones on the north.
• All gymnosperms are perennial woody plants forming either bushes or trees. Some of these are very large and live for thousand of years. e.g. Sequoia sempervirens
• All gymnosperms are perennials. They are trees or shrubs, mostly evergreen with needle-like leaves. None of the gymnosperms are herbs or annuals.
• Araucaria, a tall conifer from South America, grows well at lower altitudes and warmer climates.
• The term gymnospenn was used by Theophrastus It is smallest group in plantae with 70 genus and 900 living species. In India, 14 genus and 54 species are found.
• Roots of some gymnosperms have symbiotic relations with algae (e.g. coralloid roots of Cycas) or fungi (e.g. mycorrhizae in Pinus)
• Stem of Cycas is unbranched and in Zamia it is tuberous.
• Plants are predominantly woody, wood may be pycnoxylic (i.e., compact and hard) e.g. Pinus and other genera or it may be manoxylic (i.e. loose and soft) e.g. Cycas.
• Xylem lacks vessels (i.e. wood is nonporous) and phloem lacks companion cells. However in some plants vessels are present e.g. Gnetum, Ephedra, Welwitschia etc.
• Wood of Conifers is of great commercial importance. A good quantity of timber obtained from the species of Pinus, Cedrus, Abies etc. is used for making building arti-cles, furniture, railway sleepers, carriages etc.
• The wood of Juniperns virginiana is used for making pencils of high quality and its oil, called Red Cedar Wood oil, is used for clearing microscopic sections and for oil immersion lenses.
• All gymnosperms are perennial woody plants forming either bushes or trees. Some of these are very large and live for thousands of years. e.g. Sequoia sempervirens
• The term 'gymnosperm' was used by Theophrastus in his book "Enquiry into Plants".
• It is smallest group of plantae with 70 genus and 900 living species. In India 14 genus and 54 species are found.
• Leaves are generally dimoprphic, foliage and scale leaves.
• Foliage leaves do not have lateral veins. Transfusion tissue (hydrostereom) occurs internally for lateral transport.
• In some gymnosperms e.g. Ephedra, only scaly leaves are present.
• Wood is homoxylous but Gnetales bear vessels in xylem e.g. Ephedra, Gnetum, Welwitschia.
• Types of wood:
(i) Manoxylic: Soft wood, vascular tissues with medullary rays, commercially less important e.g. Cycas.
(ii) Pycnoxylic: Compact wood without or with narrow medullary rays, commerciallly more important e.g. Pinus.
(iii) Monoxylic: with single persistant cambium rings and bundles e.g. Pinus.
(iv) Polyxylic: With many persistant cambium rings and bundles e.g. Cycas.
• Conifers are the main sources of various types of resins which are insoluble in water but soluble in some organic solvents. Resins are used in the manufacture of varnishes, paints, medicines etc.
• Alkaloid ephedrine obtained from the species of Ephedra is used to cure cough, bronchitis, asthma etc.
• In some gymnosperms e.g. Ephedra foliata, Ephedra intermedia, bisporangiate cones can be seen.
• Male cones of gymnosperms are usually short lived.
• In Gnetales the ovules are bitegmic.
• Male gametes of Cycas and Ginkgo are motile.
• The embryo is endoscopic and there is tendency of polyembryony.
• In gymnosperms flowers are absent.
• Living fossils – Cycas, Ginkgo
• The endosperm in gymnosperms is haploid.
• Pollination is anemophilous .i.e. by wind
• Endosperm develops before fertilisation and is haploid.
• Polyebryony is of common occurrence.
• Characters common in fern and Cycas – circinate vernation and compound leaves.
• The largest size of male gamete is found in Cycas.
• Diploxylic vascular bundles are found in Cycas.
• The tissue between the pollen chamber and archegonial chamber of Cycas is neck canal cells.
• The microsporangia in Cycas microsporophylls are present on abaxial (lower) surface
• The position of microsporangia on the microsporophyll of Pinus is abaxial.
• If you are asked how many fruits are produced by single cone of Pinus. Answer is None
• Pinus – Pycnoxylic
• Nonporous wood – Pinus
• Polycotyledonous embryos are found in Pinus.
• Constituent of phloem of Pinus – sieve tubes and phloem parenchyma only.
• Gymnosperm said to have double fertilization- Ephedra.
• Gnetum shows the complete absence of archegonia in their ovule.
• Female gametophyte is tetrasporic in origin in Gnetum and Welwitschia.
• The syndetochelic stomata differs from haplochelic stomata in respect to their morphology and ontogeny.
• Podocarpus is regarded as living cordate
• Beck proposed the creation of group Progymnosperms
• Smallest gynmosperm = Zamia
• Largest gynmosperm = Sequoiadendron
• The three generations in seed are : (i) Testa. tegmen and perisperm represent parental sporophyte. ii) Endosperm represents female gametophyte ; (iii) Plumule, radicle, suspensor and cotyledons (embryo) represent future sporophyte.
• Polyembryony: It is the formation of more than one embryo inside a single seed. It was reported by Leewenhoek in oranges. Simple polyembryony is due to fertilisation of many eggs e.g. Pinus ovule has 2-8 archegonia. Cleavage polyembryony is true polyembryony and very common. It is due to splitting of embryo tissue. Adventive polyembryony is the formation of extra embryos directly from diploid cells (e.g.. rosette cells) other than embryonal cells.
• Drug ephedrine is obtained from Ephedra which is used in curing respiratory ailments including asthma.
• Ginkgo biloba is known as ‘maiden hair tree’ and ‘Pagoda tree’ and produce ciliated sperms.
ECONOMIC IMPORTANCE OF GYMNOSPERMS
Gymnosperms are economically very important. The mem¬bers of this group are variously used by human beings as food, as medicines, as plants for decoration and in industries.
Economic importance of cycadophytae
1. Ornamental value
They look like palm tree and are evergreen in nature. Foliage leaves of some species, i.e., C. revlluta, C. circinalis, C. rumphii and C. beddomei are used for decoration purposes as they remain fresh for long period.
2. Food value
Different parts of the Cycas plants are used as food material.
(i) Stem portion of C. revoluta and C. circinalis is a good source of ‘Sago’, a kind of starch used in making bread by poor people.
(ii) Pith of the plant Encephlartos is used in the preparation of Kaffer bread.
(iii) Seeds and seed kernels of some species of Cycas are roasted and taken as food.
(iv) Leaves: Young succulent leaves of some species of Cycas are cooked as vegetable.
(v) Seeds and stem of Cycas revoluta are used in making wine in Japan.
(vi) Zamia is rich in starch and is used as food by many Indians.
3. Medicinal value
Many useful medicines are prepared and extracted from the different parts of the Cycas plants.
(i) Leaves: The leaves of C. circinalis are medicinally very important. The fresh juice extracted from the leaves is used as medicine in stomach disorders, blood vomiting and other skin diseases.
(ii) Seeds and megasporophylls: Seeds and crushed bark of Cycas and its megasporophylls when mixed with coconut oil are used as poultice for sores and wounds in South India.
(iii) Pollen grains of some Cycas plants are reported to have some narcotic effect.
Economic importance of coniferophytae
The many useful products come from conifers. Papers and other products, such as the lumber used to build homes, come from conifers. Conifers are also used to make the rayon fibres in clothes, cellophane food wrappers and turpentine.
1. Ornamental value
Almost all the members are of ornamental value. Ginkgo biloba is often named as ‘Maiden Hair Tree’ because of its beautiful leaves. Thuja, Araucaria, Abies, Cryptomeria, Pinus, Taxus are grown in parks.
2. Edible value
(i) Seeds: Seeds of some species are edible, e.g., Pinus gerardiana (chilgoza), P. edulis, P. pinea. Seeds of Gnetum gnemon are also edible. Seeds of Ginkgo biloba are nutritious.
(ii) Shoots: Shoots and inflorescence of Gnetum sps are widely used as vegetables in many countries.
3. Medicinal value
(i) Gnetum ula is a common source of edible oil. It is also used as massage in rheumatic pain. A volatile oil extracted from the shoots and leaves of Thuja is used as vermifuge. Oil of Juniperus species is medici¬nally important.
(ii) Leaves: Leaves and seeds of Taxus are used as medi¬cines.
(iii) A medicine of cancer called ‘Taxol’ is obtained from the bark of Taxus.
(iv) An important alkaloid ‘ephedrine’ is obtained from Ephedra, used in treatment of asthma, cough, cold and other respiratory disorders.
4. Industrial use
Wood: Some of the important conifers like spruce or Picea (maximum cellulose content) are an important source of pulp wood and are used in manufacture of paper P. markussii is a valuable source of raw material. Timber is also obtained from various conifers. Pinus (chir), Abies (fir), Cedrus (cedar and deodar), Sequoia (red wood) are the chief source of various types of wood. The wood of Juniperus is used in making pencils, scales and holders. The wood of Biota (Thuja) is soft, brittle and durable. Woods of many conifers is used in the manufacture of paper. eg. Pinus. Conifers are the source of soft wood for construction, packing and plywood industry eg. Cedrus, Agathis
Turpentine is obtained from the resin of Pinus. It is used as solvent in paint and polishes. It is also used medicinally for pain, bronchitis etc. Saw dust of conifers is used in making linoleum and plastics. Pinus species yield a resin called rosin which is used in water proofing and sealing joints.
CLASSIFICATION OF GYMNOSPERMS
Chamberlain (1934) has classified gymnosperms into two classes 1. class Cycadophyta 2. Class Coniferophyta .
I. Cycadophytae
Divided into 3 orders:
1. Cycadofilicales or Pteridospermales or Pteridosperms (Seed ferns)
These are fossils. They show some characters of ferns and some of gymnosperms. Their origin is in late palaeozoic. These are the connecting link between pteridophytes and gymnosperms, e.g., Medullosa and Lyginopteris.
2. Bennettitales or Cycadaeodales or fossil cycads- Their leaf bases are permanently attached to stem, e.g. Williamsonia and Williamsoniella.
3. Cycadales or Living cycads- They have typical palm-like appearance. Stem is un¬branched, leaves large and male gametes are ciliated, wood is manoxylic, e.g. Cycas, MicroCycas, Zamia, Stangeria, etc. Zamia pygmaea is the smallest gymnosperm (25 cm in height).
II. Coniferophytae
The class Cycadophyta consists of plants with simple stem, thick cortex but thin wood and simple sporophylls. The class Coniferophyta consists of plants with profusely branched stem, thin cortex, thick wood and complex sporophylls. Divided into 4 orders:
1. Cordaitales- Fossils, e.g., Cordaites and Poroxylon.
2. Ginkgoales- Many fossils and a single living genus, i. e., Ginkgo biloba. which is commonly known as ‘Maiden Hair Tree’ (because of the resemblance of its leaves with those of ‘Maiden Hair Fern’ or Adiantum). It is also called ‘Living fossil’ (because single living genus in a big fossilized order). Kaemfer (1690) studied this maiden hair tree and named it as Ginkgo.
3. Coniferales
It is the largest order of modem gymnosperms. Here wood is pycnoxylic, stem branched, foliage leaves simple and reduced, called needles, e.g.. Pinus (pine), Podocarpus. Thuja (Biota), Sequoia (red wood tree), Araucaria (Christmas tree or Monkey's puzzle), Cupressus, Picea (spruce), etc. Sequoia is the largest gymnosperm (366 ft in height).
4. Gnetales
It is the highest order of gymnosperms and is a connect¬ing link between gymnosperms and angiosperms. This order is peculiar as it has 3 genera, which are quite different from each other.
e.g., Gnetum, Ephedra (Jointed fir) and Welwitschia. This is the only order in gymnosperms where vessels are present in xylem.