Dear Student,
Epidermis is the plant tissue, which forms the outermost layer and covers the whole plant body. They form the outermost covering of all plant structures. They are mostly a single layer of cells (but can be multilayered also).
The main function of epidermis is protection. A waxy, water-resistant layer is present on the upper parts of plants. This layer prevents loss of water from leaves and stems, mechanical injury and infection from parasites.
Regards