Many plant parts have an epidermis. It is the outermost layer of cells of young plant parts; on roots, some cells differentiate into root hairs, on stems and leaves into hairs of various kinds (pubescence) and on leaves, stems and berries into stomata.
Plant hairs (botanically called trichomes) may be present on stems or leaves. They are prolonged epidermal cells; on a stem or leaf it may be living or dead, deciduous or persistent; on a root it is short-lived and confined to the absorbing zone, called a “root hair”.
Leaves or stems without hairs are called glabrous. Pubescent plant parts are covered in short, fine, soft hairs. Tomentose parts have a hairy covering of short, closely matted hairs.