Question

Cell wall of lignified cell is
(a) Semipermeable and dead
(b) Permeable and dead
(c) Impermeable and dead
(d) Impermeable and living

Answer 1

Hint: The polysaccharide components of plant cell walls are highly hydrophilic (water loving), whereas lignin is more hydrophobic (water hating). Lignified cells have a large amount of deposition in the cell wall.

Complete Answer: Cell wall of a lignified cell is Impermeable and dead. Lignified cells refer to the condition of the cell wall when a large amount of lignin is deposited in the cell wall of a certain cell. Lignin is a crucial organic polymer which is abundant in cell walls of some specific cells. As they are dead, they cement together and anchor the cellulose fibres of the cell wall giving it a rigid and woody structure. It shows hydrophobic properties, which means they do not mix with water and are impermeable.
Lignin fills the spaces within the cell wall between cellulose, hemicellulose, and pectin components, especially in vascular and support tissues: xylem tracheids, vessel elements and sclereid cells. It is covalently linked to hemicellulose and thus cross- links different plant polysaccharides, conferring mechanical strength to the cell wall and by extension the plant as an entire.
Function of lignin are:
- Lignin plays a vital function in the growth and development of plants.
- Lignin increases plant cell wall rigidity, as they are a complex phenolic polymer.
- It shows hydrophobic properties and promotes minerals transport through the vascular bundles in plants.
- Lignin metabolism can also be actively mixed up in plant lodging resistance and in reaction to various environmental stresses.

So, the correct answer is ‘Impermeable and dead’.

Note: Lignin is an important barrier that protects against pests and pathogens. Global commercial production of lignin is a consequence of papermaking. The study of lignin biosynthesis and its function will have a big impact on industrial, agricultural production and other human activities.