Opening and closing of stomata:

                           The stomata are the main pathway of transpiration, photosynthesis, and respiration. Stomata are minute pores found in the epidermis of aerial parts mainly in leaves. They are absent in roots and non-greenpartst plants not. Stomata are surrounded by two guard cells that control the opening and closing of stomata. The opening and closing of stomata depend upon heat, light, humidity, and water contents of the cell. The walls of the guard cells are thick towards the sides of the pores and thin on the other side. When the guard cell gains water, it becomes turgid and the outer wall of the guard cell stretches outwards, causing outward stretching of the inner wall. The inner wall becomes inelastic and forms a concave shape as a result stomata opens. The decrease in turgor pressure in the guard cell causes the closing of the stomata in the reverse way.