the epidermis in plants is a single layer of cells. it covers the leaves, flowers, roots and stems of plants. it divides the plant from the outside environment. the epidermis has more than one function. it protects the plant from loss of water. it controls gas exchange. it makes metabolic compounds. in the roots it takes in water and nutrients. some parts of a plant may have a different cover called a periderm. potatoes have that kind of covering.