It is usually present in the outermost layer of the plant body such as leaves, flowers, stem and roots.
Structure:
Epidermis is one cell thick and is covered with cuticle.
Cuticle is a water proof layer of a waxy substance called cutin.
It forms a continuous layer without intercellular spaces.
Most epidermal cells are relatively flat.
Function:
The main function of epidermis is to protect the plant from desiccation and infection.
Cuticle of epidermis helps to reduce water loss by evaporation from the plant surface.
This aids in protection against loss of water, mechanical injury and invasion by parasitic fungi.
In some plants living in very dry habitats, the epidermis may be thicker since protection against water loss is critical.
Stomata:
Epidermis of a leaf is not continuous at some places due to the presence of small pores, called stomata.
Each stoma is bounded by a pair of specialised epidermal cells or two kidney-shaped cells called guard cells.
Function of Stoma: The stoma allows gaseous exchange to occur during photosynthesis and respiration.
Cork:
As plants grow older, the outer protective tissue undergoes certain changes.
A strip of secondary meristem, replaces epidermis of stem.
Ultimately becomes several layered thick cork (bark) of trees.
The cork cells do not contain protoplasm but are filled with resin or tannins.
Structure:
Cells of cork are dead and compactly arranged without intercellular spaces
Suberin: Suberin deposits are organic, fatty substances which form the heavily thickened walls of cork cells. Suberin makes the plants impervious to gases and water.
