Question

The wall-thickening material in tracheids and vessels are

• A. Cutin and suberin
• B. Cellulose and cutin
• C. Suberin and cellulose
• D. Lignin and cellulose

Answer 1

The correct option is D Lignin and cellulose

The cells cease to increase in size and become mature. At this stage, the cells become modified according to the function they have to perform. During the process of their maturation, the cells undergo additional or secondary thickening deposition of new materials such as cellulose, lignin, suberin, cutin, etc. The cells of certain parts (e.g., pericycle, phloem, xylem, etc.) of the plants undergo heavy thickening of their walls. The thickening materials of the cells are secreted by the protoplasm. These materials are deposited in the cell walls in such manner that cell wall becomes stratified in appearance. The cells which ultimately develop into vessels, tracheids and fibres show the thickening of the cell wall in various ways. This thickening takes place due to the deposition of a hard substance, called lignin, on the inner surface of the cell wall. Usually the thickening material (e.g., lignin) of the secondary wall is not laid down in uniform thickness but it may form the special patterns such as annular, spiral, scalariform, reticulate and pitted.

So the correct option is Lignin and cellulose