Question

Cell wall of sclerenchymatous fibres and sclereids are respectively thickened by
A) Cellulose , cellulose
B) Cellulose , hemicellulose
C) Lignin , cellulose
D) Lignin , lignin

Answer 1

Hint:Cell wall is a structure found outside the membrane of the cell.Cell wall is dead and the cell wall is completely permeable.The function of cell wall is to maintain the structure of the cell and provide protection.Cell wall is absent in Animals.A cell wall is present in plants and fungi.But it is made of different substances.


Complete answer:

>There are two types of cells.Meristematic and permanent.Permanent are the cells which are formed by meristematic cells.
>Sclerenchyma consists of long , narrow cells with thick and lignified cell walls having a few or numerous pits.
>They are usually dead and without protoplast.On the basis of variation in the form , structure , origin and development.Sclerenchyma may be either fibres or sclereids.
>The fibres are thick walled , elongated and pointed cells generally occurring in groups in various parts of the plant.The cell wall is thickened by the deposition of lignin.
>The sclereids are spherical , oval or cylindrical , highly thickened dead cells with very narrow cavities known as lumen.The cell wall of sclereids are also thickened by lignin.

So the correct answer is ( D ).

Note:Sclerenchyma provides mechanical support to organs of plants.As there cell walls are lignified.The commonly found in the fruit walls of nuts , pulp of fruits like Guava , pear and sapota , seed coat of legumes in leaves of tea.