Question

In which of the following sclerenchyma cells, the secondary cell walls are present
A. The cells containing cytoplasm only
B. The cells with protoplast
C. Cells which are living at maturity
D. Cells which are non-living at maturity

Answer 1

Hint: Sclerenchyma is hard supporting tissue, formed of long narrow, fibre-like cells with pointed ends. Sclerenchyma occurs in roots, stem, leaves and petiole, associated with the vascular tissues, and in the cortex. The sclerenchyma cells may form patches or arranged in layers. These are of two types namely fibres and sclereids.

Complete answer:
Characteristics of Sclerenchyma
Sclerenchyma cells are dead, without nucleus and cytoplasm.
Their cell wall is formed of cellulose and hemicellulose.
It is thickened due to the secondary deposition of lignin (i.e., have lignified cell walls).
Lignin acts as a cement and hardens the cell wall.
The lignified cell wall has pits.
Now let us match this with given options:-
The cells containing cytoplasm only :- sclerenchymatous cells do not contain cytoplasm so they are dead. Thus this option is not correct.
The cells with protoplast:- sclerenchymatous cell at first contains protoplasm it loses protoplasm when it reaches maturity. Hence this option is not correct.
Cells which are living at maturity :- these cells are dead at maturity and not living because loss of protoplasm occurs. Thus this option is not correct.
Cells which are non-living at maturity :- sclerenchymatous cells lose protoplasm at maturity and deposit lignin as secondary wall. Thus this option is correct.

Our required Ans is d that is Cells which are non-living at maturity.

Note: Lignin is a complex polymer of amino acids deposited in the cell wall of plant cells. It provides flexibility, great tensile and compressional strength. Lignin makes the cell wall impermeable and does not allow substances to pass through it. As a result heavily lignified cells (such as sclerenchyma cells) are without living cytoplasm.