Write a note on Epidermal Tissue system.

Explanation

On the of their structure and location, these are three types of tissue system : Epidermal tissue system, the ground or fundamental tissue system and the vascular or conducting tissues system.
Epidermal Tissue System :
The epidermal tissue system forms the outermot covering of the whole plant body and comprises epidermal cells, stomata and the epidermal appendage - the trichomes and hairs.
The epidermist of outermost layer of the primary plant body. It is made up of elongated, compactly arranged which form a continuous layer.
Epidermis is usually single layered. Epidermal cells are parenchymatous wiht a small amount of cyptoplasm lining the cell wall and a large vacuole.
The outside of the epidermis is often covered with a waxy thick layer called the cuticle which prevents the loss water.
Cuticle is absent in roots.
Stomata are structures present in nthe epidermals of leaves. Stomata regulate the process of traspiration and gaseous exchange.
In dicot plants, each stoma is composed of two bean-shaped cells known as guard cells.
In grasses, the guard, cells are dumb-bell shaped. The outer walls of guard cells (away from the stomatal pore) are thin and the inner walls (towards the stomatal pore) are highly thichened.
The guard cells possess chloroplast and regulate the opening and closing of stomata.
Sometimes, a few epidermal cells, in the vicinty of the guard cells become specialised in their shape and size and are known as subsidary cells.
The stomatal aperture, guard cells and the surrounding subsidary cells are together called stomatal apparatus.
The cells of epidermis bear a number of hairs. The root hairs are unicellular elongations of the epidermal cells and help absorb water and minerals from the soil.
On the stem the epiudermal hairs are called trichomes. The trichomes in the shoot system are unually multicellular. They may be branched or unbbranched and soft or stiff. They may even be secretory.
The trichomes help in preventing water loss due to transpiration.