Tiny holes present in leaves are called Stomata. Singular form of Stomata is Stoma. Stomata mostly present in the lower surface of leaves and on green stems. These play an important role in the process of photosynthesis and help in maintaining the water balance of the plant.
A Stoma has two bean-shaped cells. These cells are 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 outwords and the Stomata open. When the guard cells lose water, they lose their turgidity and the Stomata close. Normally Stomata remain open during the day and close at night.
