Epidermis and Cork Cells in Plants
The epidermis is usually made of a single layer of cells. The entire surface of a plant has this outer covering of epidermis. Cork cells are dead and do not have any intercellular spaces. The walls of these cells are heavily thickened by the deposition of suberin. In some plants living in very dry habitats, the epidermis may be thicker since protection against water loss is critical. It protects all the parts of the plant. Epidermal cells on the aerial parts of the plant often secrete a waxy, water-resistant layer on their outer surface. This aids in protection against loss of water, mechanical injury and invasion by parasitic fungi. Since it has a protective role to play, cells of epidermal tissue form a continuous layer without intercellular spaces. Most epidermal cells are relatively flat. Often their outer and side walls are thicker than the inner wall (Watch Epidermis and Cork Cells Video to learn more).
Small pores are present in the epidermis of the leaf. These pores are called stomata. Stomata are enclosed by two kidney-shaped cells called guard cells. They are necessary for exchanging gases with the atmosphere. Transpiration (loss of water in the form of water vapour) also takes place through stomata.
Epidermal cells of the roots, whose function is water absorption, commonly bear long hair-like parts that greatly increase the total absorptive surface area. In some plants like desert plants, epidermis has a thick waxy coating of cutin (chemical substance with waterproof quality) on its outer surface. As plants grow older, the outer protective tissue undergoes certain changes. A strip of secondary meristem replaces the epidermis of the stem. Cells on the outside are cut off from this layer. This forms the several-layer thick cork or the bark of the tree. Cells of cork are dead and compactly arranged without intercellular spaces. They also have a chemical called suberin in their walls that makes them impervious to gases and water.
Epidermis and Cork Cells Video
Useful for CBSE, ICSE, NCERT & International Students
Grade : 9
Subject : Biology
Lesson : Tissues
Topic: Epidermis and Cork Cells
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