Question

What are permanent tissues? Describe the different types of simple permanent tissues.

[Review question: Pg. No: 224]

Answer 1

Permanent Tissues:
Permanent tissues are those in which, growth has stopped either completely or for the time being. At times, they become meristematic partially or wholly. Permanent tissues are of two types, namely: simple tissue and complex tissue
Simple Tissues:
Simple tissues are homogeneous tissues composed of structurally and functionally similar cells. eg., Parenchyma, Collenchyma and Sclerenchyma.
Parenchyma:

• Parenchyma are simple permanent tissues composed of living cells.
• Parenchyma cells are thin walled, oval, rounded or polygonal in shape with well developed spaces among them.
• In aquatic plants, parenchyma possesses intercellular air spaces, and is named as Aerenchyma.
• When exposed to light, parenchyma cells may develop chloroplasts and are known as Chlorenchyma.
• Parenchyma may store water in many succulent and xerophytic plants. It also serves the functions of storage of food reserves, absorption, buoyancy, secretion etc.,

Collenchyma:
Collenchyma is a living tissue found beneath the epidermis. Cells are elongated with unevenly thickened walls. They provide mechanical support for growing organs.
Collenchyma
Sclerenchyma:

1. Sclerenchyma consists of thick walled cells which are often lignified.
2. Sclerenchyma cells are dead and do not possess living protoplasts at maturity.
3. Sclerenchyma cells are grouped into fibres and sclereids.