Question

Rapid and irreversible cell elongation occurs commonly in plants but not in animals. This difference is due to the.

• A. Presence of chloroplasts and mitochondria
• B. Absence of centrioles and Golgi bodies
• C. Absence of endoplasmic reticulum and presence of large vacuoles
• D. Presence of large vacuoles and cell walls

Answer 1

The correct option is D Presence of large vacuoles and cell walls

A plant cell wall is arranged in layers and contains cellulose microfibrils, hemicellulose, pectin, lignin, and soluble protein.

-Irreversible cell expansion is an essential aspect of plant growth and morphogenesis.

-Surface expansion of the cell wall may be highly localised, as in tip‐growing cells, or more evenly dispersed over the cell wall surface (‘diffuse growth’), occurs pattern common in most cells of the plant body.

-Most cells undergo a relatively brief period of rapid cell expansion after they leave the meristem and before they differentiate into mature cells.

-Expansive growth of plant cells requires simultaneous uptake of water into the cell and irreversible expansion of the cell wall.

-Cell growth begins with cell wall loosening which leads to ‘stress relaxation’ of the cell wall which in turn creates the water potential difference needed for water uptake by the cell, resulting in the physical enlargement of the cell.

-The growing cell wall is composed of a network of cellulose microfibrils embedded in pectins and hemicelluloses that make up the wall matrix; these materials combine to form a load‐bearing structure that controls cell mechanics and physically limits cell growth.

So, the correct option is 'D'.