Reproduction (Plants) – Pre-fertilisation: NEET MCQs with Answers

15 free questions on Reproduction (Plants) – Pre-fertilisation for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Pre-fertilisation: Structures and Events: Outbreeding devices; Pollen-Pistil interaction

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Question 1

Previous-year question
Unisexuality of flowers prevents [AIPMT 2008]
  1. autogamy, but not geitonogamy
  2. both geitonogamy and xenogamy
  3. geitonogamy, but not xenogamy
  4. autogamy and geitonogamy
Show answer
Answer: (A) autogamy, but not geitonogamy
Explanation: A unisexual flower has only stamens or only carpels, so pollination within the same flower (autogamy) is impossible. If the plant is monoecious, pollen can still pass from a male flower to a female flower of the same plant, so geitonogamy is not prevented.

Question 2

Previous-year question
Transmission tissue is characteristic feature of [AIPMT 2015 Cancelled]
  1. dry stigma
  2. wet stigma
  3. hollow style
  4. solid style
Show answer
Answer: (D) solid style
Explanation: Transmission tissue is a specialised nutritive tissue located in the centre of a solid style. Its cells are connected by plasmodesmata and they nourish and guide the pollen tube on its way to the ovary.

Question 3

Previous-year question
Which of the following statements is not correct? [NEET 2016, Phase II]
  1. Insects that consume pollen or nectar without bringing about pollination are called pollen nectar robbers
  2. Pollen germination and pollen tube growth are regulated by chemical components of pollen interacting with those of the pistil
  3. Some reptiles have also been reported as pollinators in some plant species
  4. Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grows into the style
Show answer
Answer: (D) Pollen grains of many species can germinate on the stigma of a flower, but only one pollen tube of the same species grows into the style
Explanation: Pollen of different species is incompatible and normally fails even to germinate on the stigma. Only pollen of the same species is recognised and accepted, germinates and forms pollen tubes that grow through the style — this recognition is the essence of pollen–pistil interaction.

Question 4

Previous-year question
A dioecious flowering plant prevents both [NEET 2017]
  1. autogamy and xenogamy
  2. autogamy and geitonogamy
  3. geitonogamy and xenogamy
  4. cleistogamy and xenogamy
Show answer
Answer: (B) autogamy and geitonogamy
Explanation: In a dioecious plant the male and female flowers occur on different individuals, so a plant carries only one sex. This prevents autogamy, which needs a bisexual flower, and geitonogamy, which needs both sexes on the same plant, while still permitting xenogamy.

Question 5

Previous-year question
In which of the following, both autogamy and geitonogamy are prevented? [NEET 2019, 2012]
  1. Wheat
  2. Papaya
  3. Castor
  4. Maize
Show answer
Answer: (B) Papaya
Explanation: Papaya is dioecious — male and female flowers are borne on separate plants. Since a single plant bears only one sex, neither autogamy (self-pollination within a flower) nor geitonogamy (between flowers of the same plant) is possible. Castor and maize are monoecious, so geitonogamy can still occur.

Question 6

Previous-year question
Both autogamy and geitonogamy are prevented in [2011]
  1. castor
  2. papaya
  3. maize
  4. cucumber
Show answer
Answer: (B) papaya
Explanation: Papaya is dioecious, male and female flowers being borne on separate plants, so no pollen can reach a stigma on the same plant and only xenogamy is possible. Castor, maize and cucumber are monoecious, which prevents autogamy but still permits geitonogamy.

Question 7

Previous-year question
Fertilisation in which the male gametes are carried by a pollen tube is called [1993]
  1. chalazogamy
  2. porogamy
  3. syngonogamy
  4. siphonogamy
Show answer
Answer: (D) siphonogamy
Explanation: Siphonogamy is fertilisation effected through a pollen tube, and it is what freed the seed plants from any dependence on external water. Porogamy and chalazogamy describe only the point at which the tube enters the ovule, not the mechanism itself.
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Question 8

Previous-year question
The entry of the pollen tube through the micropyle is called [1991]
  1. porogamy
  2. chalazogamy
  3. pseudogamy
  4. mesogamy
Show answer
Answer: (A) porogamy
Explanation: Porogamy is the normal route, the tube passing through the micropyle. In chalazogamy, seen in Casuarina, it enters through the chalaza, and in mesogamy it forces its way through the integuments or the funicle. Pseudogamy is a quite different phenomenon in which pollination stimulates development without fertilisation.

Question 9

Previous-year question
In angiosperms the pollen tube liberates its male gametes into the [2001]
  1. egg cell
  2. central cell
  3. synergids
  4. antipodal cells
Show answer
Answer: (C) synergids
Explanation: The pollen tube enters one of the two synergids through the filiform apparatus and discharges both male gametes into it. From there one gamete moves to fuse with the egg and the other with the two polar nuclei of the central cell.

Question 10

Previous-year question
In which one of the following, both autogamy and geitonogamy are prevented? (NEET UG 2019)
  1. Maize
  2. Wheat
  3. Papaya
  4. Castor
Show answer
Answer: (C) Papaya
Explanation: Papaya is dioecious (separate male and female plants), so both autogamy and geitonogamy are prevented.

Question 11

Previous-year question
A dioecious flowering plant prevents both: (NEET UG 2017)
  1. Cleistogamy and xenogamy
  2. Autogamy and xenogamy
  3. Autogamy and geitonogamy
  4. Geitonogamy and xenogamy
Show answer
Answer: (C) Autogamy and geitonogamy
Explanation: A dioecious plant has male and female flowers on SEPARATE individuals — preventing both autogamy (within a flower) and geitonogamy (between flowers of the same plant).

Question 12

In most flowering plants the pollen tube enters the ovule through the micropyle, but in Casuarina it enters through the chalaza and in Cucurbita it passes through the integument. Despite these different routes, how does the tube normally reach the inside of the embryo sac?
  1. It fuses directly with the wall of the egg cell
  2. It enters through the side wall of the central cell
  3. It enters at the chalazal end by passing between the antipodal cells
  4. It enters at the micropylar end, into a synergid through the filiform apparatus
Show answer
Answer: (D) It enters at the micropylar end, into a synergid through the filiform apparatus
Explanation: The point of entry into the ovule varies, but the entry into the embryo sac does not. The tube is guided to the micropylar end by the filiform apparatus of the synergids and discharges into one synergid. The male gametes then move from there to the egg and the central cell.

Question 13

A student wants to watch pollen tubes emerge from balsam pollen in the school laboratory. Which set-up is most suitable?
  1. Pollen placed in concentrated hydrochloric acid on a slide and observed immediately
  2. Pollen kept dry on a clean slide in the dark and observed under low power after 24 hours
  3. Pollen dusted on a drop of about 10% sugar solution on a slide, observed under low power after 15 to 30 minutes
  4. Pollen boiled in distilled water, stained, and observed under high power after 2 to 3 days
Show answer
Answer: (C) Pollen dusted on a drop of about 10% sugar solution on a slide, observed under low power after 15 to 30 minutes
Explanation: Pollen germinates readily in a dilute sugar solution, which supplies nutrition and a suitable osmotic environment. Pollen tubes can be seen on a slide within about 15 to 30 minutes under the low power of a microscope. Boiling kills the pollen, while dry conditions and strong acid do not support germination.

Question 14

A breeder collects wheat pollen in the morning, leaves it on a laboratory bench, and dusts it on emasculated wheat flowers in the evening. No seed forms. The same routine works with pollen of a legume known to stay viable for months. What is the most likely reason for the wheat failure?
  1. Wheat stigmas become receptive only to pollen of a different species
  2. Wheat pollen tubes can grow only in the presence of insect pollinators
  3. Wheat pollen is shed before meiosis has been completed in the anther
  4. Wheat pollen loses viability within about 30 minutes of release
Show answer
Answer: (D) Wheat pollen loses viability within about 30 minutes of release
Explanation: Pollen viability varies widely among species. In cereals such as rice and wheat, pollen stays viable for only about 30 minutes after release, whereas some legumes keep it for months. Pollen left on a bench all day would therefore be dead by evening. Such pollen would have to be stored in liquid nitrogen or used quickly.

Question 15

A single castor plant and a single female papaya plant are each grown far from any other plant of their species, with wind and insects available. Assuming the castor plant is self-compatible and neither plant shows apomixis or parthenocarpy, which outcome is expected?
  1. Castor can set seed through geitonogamy, but the female papaya plant cannot set seed
  2. Papaya can set seed through autogamy, but the castor plant cannot set seed
  3. Neither plant can set seed, because both bear unisexual flowers
  4. Both plants set seed through geitonogamy
Show answer
Answer: (A) Castor can set seed through geitonogamy, but the female papaya plant cannot set seed
Explanation: Castor is monoecious, so pollen can pass from a male flower to a female flower on the same plant, which is geitonogamy. Papaya is dioecious, so a female plant has no anthers at all and needs pollen from a separate male plant. Unisexual flowers rule out autogamy in both, but only dioecy also rules out geitonogamy.

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