Opening and closing of stomata:

                           The stomata are the main path way of transpiration, photosynthesis and respiration. Stomata are minute pores found in epidermis of aerial parts mainly in leaves. They are absent in roots an non-green part of plant.Stomata are surrounded by two guard cells that controls the opening and closing of stomata. The opening and closing of stomata depends upon heat, light, humidity and water contents of the cell. The wall of guard cell are thick towards the sides of pores and thin in other side. When guard cell gain water, it become turgid and the outer wall of guard cell stretch outwards, causing outward stretching of their inner wall. The inner wall become inelastic and form a concave shape as a result stomata opens. The decrease in turgor pressure in guard cell cause the closing of stomata in reverse way.

Fig: Closed type stomata

Fig: Open type stomata