Collenchyma, part of the ground tissue, is a simple living tissue found in plants. Collenchyma layer is generally found below epidermis of the plant. They are either found in a patch manner or even distributed throughout. The cell wall of collenchyma tissue cells is thickened at corner due to higher deposition of cellulose, pectin and hemicellulose. The cells are generally spherical or polygonal in shape. This tissue provides mechanical support to the young stem and leaf.
Parenchyma is a type of simple permanent tissues forming a major component of the tissues of plant. These cells are in various shapes like oval, round, polygonal etc. with a thin cell wall made of cellulose. These cells perform functions like storage, photosynthesis, secretion.
The simple permanent tissue consisting of dead cells without protoplast is called sclerenchyma. These cells are long and narrow with lignified cell wall. The thick-walled, elongated pointed cells form the sclerenchyma fibres and the spherical, oval shaped cell with highly thickened cell wall and narrow cavity form the sclerenchyma sclereids.