Epidermis is the outer layer of plant covering plant surface, such as roots, or leaves, It consist of tightly composed one layer flat cell with no intercellular air space. The generally function of epiderm tissues is to protect the underlying cells.
Epidermis has several different modification and function, such as hair, spine, trichome, stomata lenticell, root hair, cuticule or waxy layer.
On the old woody plants, the epidermis of stem is replaced by periderm which is composed of cork tissues (phelem), cork cambium (phelogen), and phelodrem, Phelodrem. Phelogen is formed beneath or within the epidermis. Phelem and pheloderm are formed from phelogen tissues activities. The tissue wall of phelem contains cork substances (suberin).