Anatomy of Flowering Plants – The Tissues: NEET MCQs with Answers

Explanation: Collenchyma cells are thickened at the corners due to deposition of cellulose, hemicellulose and pectin, so Statement I is true. Sclerenchyma cells have thick, lignified walls with few or numerous pits, so Statement II is also true.

Explanation: Companion cells help maintain the pressure gradient in sieve tubes, gymnosperms lack vessels, mature xylem vessels have no cytoplasm, and xylem fibres may be septate or aseptate, so A–D are correct. E is wrong because a mature sieve element has peripheral cytoplasm and a large vacuole but lacks a nucleus.

Explanation: The figure represents a vessel element. Vessels are long cylindrical tube-like xylem elements made of many cells (vessel members) with lignified, pitted walls and no protoplasm; the figure shows a broad member with a pitted wall and perforated oblique ends where it joins the next member. A tracheid is a single elongated cell with tapering ends and no perforated end walls. Xylem fibres are narrow with obliterated lumens, and xylem parenchyma cells are living, thin-walled cells.

Explanation: Besides water and minerals, xylem sap carries organic nitrogen compounds (such as amino acids and ureides) and hormones like cytokinins from the root to the aerial parts.

Explanation: In a solid style the central core of specialised cells, the transmission tissue, provides the nutritive path along which the pollen tube grows towards the ovary.

Explanation: Tracheids lack perforations; water passes from one tracheid to the next through pit membranes. Vessels, the other tracheary element, possess perforation plates.

Explanation: Commercial coir fibres are obtained from Cocos nucifera (coconut). They are surface fibres that occur in the fibrous mesocarp of the coconut fruit. Oak, teak and sisso are valued as timber-yielding trees rather than as fibre sources.

Explanation: The tunica-corpus theory was proposed by Schmidt in 1924 to explain the organisation of the shoot apical meristem. The tunica is the outer zone whose cells divide anticlinally and give rise to the protoderm and hence the epidermis, while the corpus is the inner zone that forms the procambium and ground meristem.

Explanation: Lateral meristems, namely the vascular cambium and the cork cambium (phellogen), are situated along the sides of the stem and root. They add secondary tissues on both sides by dividing in the radial direction and thus bring about an increase in the girth of the organ.

Explanation: The tracheary elements of the xylem become lignified and lose their protoplasm as they mature. Only after this death of the protoplast do they form continuous hollow tubes offering minimum resistance, and it is in this dead condition that they conduct water and mineral sap.

Explanation: Sieve tubes are elongated tubular channels formed by the end-to-end union of numerous cells. They have a broad lumen and thin walls, and the transverse septa between successive cells bear numerous perforations forming sieve plates, so that the organic solutes can pass readily from one element to the next.

Explanation: According to the tunica-corpus theory the distinction between the two zones rests on the planes of cell division. Cells of the tunica, the outer zone, divide only anticlinally, that is, in a plane perpendicular to the surface, whereas cells of the corpus, the inner mass, divide in various planes.

Explanation: Collenchyma is a simple permanent living tissue composed of elongated cells with thickened pectocellulosic walls. It provides both mechanical strength and elasticity and thus permits continued growth, and it occurs typically in the hypodermis of the stem and petiole of dicot herbs and in climbing stems.

Explanation: Sieve tubes are the food-conducting elements of the phloem. They possess a nucleus in the young stage but it disappears at maturity, leaving an organised and differentiated cell that retains a network of cytoplasmic strands. Vessels and tracheids are completely dead and devoid of protoplasm.

Explanation: Depending on the site of wall thickening, collenchyma is of three types. Angular collenchyma, in which thickening occurs at the angles or corners of the cells, is found in Cucurbita and marigold; lamellar collenchyma has thickening on the tangential walls, as in sunflower; and lacunate collenchyma has thickening on the walls bordering the intercellular spaces, as in Salvia.