Question

Lignin occurs in the cell walls of:
(A) Phloem
(B) Cork
(C) Woody tissue/ Xylem cells
(D) Parenchyma/ Epidermal cells

Answer 1

Hint:- The cell wall is a tough structural layer lying outside the cell membrane. It provides structural support and protection to the cell. It is present in fungi, plants and most bacterias but is absent in animals. The cell wall is made up of Cellulose, Hemicellulose and Pectin.

Complete solution:
Lignin is a complex organic molecule that plays an important part in supporting tissues of the vascular part and some algae. Lignin provides rigidity to the cell wall, hence is important in the cell wall formation of wood and bark. Plant cells consist of primary and secondary cell walls. When cells divide for the first time, a primary cell wall forms around the daughter cells and when the cell has finished growing, the secondary cell wall is formed between the cell membrane and the primary cell wall. Secondary cell wall is formed by successive layers of cellulose and lignins. Lignin fills the space in the cell wall between cellulose, hemicellulose and pectin. It is present in vascular and supporting tissues such as xylem tracheids, vessel elements and sclereids cells. Lignin helps in the transportation of water in stems. Hence, it is present in xylem cells, that's why they are heavily lignified and make up the wood of woody plants. Lignin is also present in phloem, but is present in low amounts as compared to xylem. Cork also contains lignin but the predominant material in cork is suberin. Parenchyma is a living cell, that's why Lignin is absent in parenchyma.
So, the correct answer is Option (C) - Woody tissue/ Xylem cells.

Note:- Xylem is composed of dead components, except for xylem parenchyma which is a living component. Xylem is involved in water conduction, so they require a narrow tube like structure, so that water can rise through capillary action. Lignin helps the xylem to withstand pressure changes when water moves in it.