Write a short note on stomata.

Small openings on the leaves present mostly on the lower surface of leaves and on green stems are called stomata. Each stoma has two bean-shaped cells called guard cells. The inner walls of the guard cells are thicker than the outer walls. When the guard cells are full of water, they swell and bulge outwards and the stomata opens. When the guard cells lose water, they lose their turgidity and the stomata closes. Normally stomata remains open during the day and closes at night. Stomata have following functions:

1. Exchange of gases (carbon dioxide and Oxygen)
2. Transpiration (loss of water from the plant surface)