Question

In one tissue, cells are isodiametric, walls are thin and made of cellulose, the other tissue consists of long narrow cells with thick and lignified walls. They are
a) Parenchyma and collenchyma
b) Parenchyma and sclerenchyma
c) Sclerenchyma and collenchyma
d) Sclerenchyma and Parenchyma

Answer 1

Hint: Plant tissue is broadly classified into meristematic tissue and permanent tissue. Parenchyma, collenchyma and sclerenchyma are the types of permanent tissue.

Complete Answer:
Meristematic tissue: It is a plant tissue that has the capacity to divide actively throughout its life. Meristematic tissue helps in growth and is responsible in the formation of new organs and also heals the damaged parts of the plant body.

Permanent tissue: The tissues that are completely developed and have lost the ability of division are known as permanent tissues. The meristematic tissues divide and differentiate to form the permanent tissues. It is classified into simple permanent tissue and complex permanent tissue. The simple permanent tissue is further divided into parenchyma, collenchyma and sclerenchyma.
1. Parenchyma: They are living storage tissue and most widely found tissue in the plant body and are called ground tissue.
- Cells are usually isodiametric with intercellular spaces.
- Cell wall is uniformly thin and composed of cellulose.
- Cells store substances like food, water, secretory and excretory products.
- Performs functions like photosynthesis, storage and secretion.

2. Collenchyma: It is living mechanical tissue present in the hypodermal regions of dicot stem, fruit walls and leaves.
- It is generally absent in roots and monocots.
- Cell wall is unevenly thickened with cellulose and pectin.
- Provides mechanical support to growing parts of plants like petiole of leaf and young stem.

3. Sclerenchyma: It is a dead mechanical tissue at maturity
They are of 2 types- sclerenchyma fibres and sclereids.
- The sclerenchyma fibres are elongated, spindle shaped, polygonal cells.
- Cell wall is uniformly lignified.
- Sclereids are thick walled, strongly lignified, hard cells found in pulpy fruits, petals, leaves and seed coats.

The correct answer is (b) Parenchyma and sclerenchyma.

Note: Fibres are elongated cells while sclereids are broad cells. Both fibres and sclereids are sclerenchyma cells with a thick, secondary cell wall that is lignified.