UPSC Express

Q16. Epidermis on the aerial parts of the plant often secretes a waxy layer to protect against:

A. Loss of water

B. Mechanical injury

C. Invasion by parasitic fungi

D. All of the above

Answer: D

Exp: The outermost layer of cells is known as epidermis. The epidermis is usually made of a single layer of cells. In some plants living in very dry habitats, the epidermis may be thicker since protection against water loss is critical. The entire surface of a plant has this outer covering of epidermis. 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. We can observe small pores here and there 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.