What are simple tissues ? Describe various types of simple tissues.

Explanation

The tissues which are made of only one type of cells are called simple tissues.
The various types of simple tissues are parenchyma, collenchyma and sclerenchyma.
Parenchyma :
1) The Parenchyma is a living tissue. It occupies a major part of the plant body. So it is known as fundamental tissue or ground tissue.
2) The cells are isodiametric. They may be spherical, oval round, polygonal or elongated in shape.
3) Cell walls are thin, made up of cellulose.
4) Intercellular spaces may be present or absent.
5) Parenchyma performs functions like photosynthesis, storage, and secretion.
Collenchyma :
1) Collenchyma is a living mechanical tissue:
2) It is present below the epidermis in dicot plants.
3) It is present as a continuous hypodermal ring (Eg: Helianthus annus) or as a discontinuous ring (cucurbita)
4) Corners are thickened due to cellulose, hemicellulose and pectin.
5) Intercellular spaces are absent.
6) It provides mechanical support to the growing parts of the plant parts such as young stem, petiole, pedicle etc.
7) In the cytoplasm, if chloroplast is present, photosynthetic in function.
Scelerenchyma :
1) Sclerenchyma is a dead mechanical tissue.
2) Cells are long and narrow.
3) Cell walls are thickened with legnin with pits.
4) They are dead cells. Protoplast is absent.
5) Basing upon the structure, origin and development sclerenchyma are two types - fibres, sclereids.
6) Fibres are thick walled, elongated and pointed cells.
7) Sclereids (stone cells) are spherical, oval or cylindrical shape.
8) Cell walls are highly thickened, lumen is very narrow.
9) Sclereides are found in fleshy fruits like guava, pear and sapota. Seed coat of legumes, leaves of tea, fruit wall of nuts etc.
10) Their main function is to give mechanical support.