Stomata: Some minute pores which are usually, found in leaf for the exchange of gas and transpiration are known as stomata (singular stoma).
i) Stomata are present in the green pan of leaf stem, green sepals and green outer layer of the flower.
ii) Stomata are present on the lower epidermis of dorsiventral leaves, upper and lower epidermis of isolateral leaves and partly on the floating leaves of aquatic plants.
- The stomatal pores are very minute and are covered with crescent-shaped guard cells.
- The outer wall of guard cells are thin and the inner wall is thick. Each guard cell contains cytoplasm, a nucleus and plenty of chloroplasts.
- There is a single large air chamber below the stomatal pore.
Functions of stomata:
- The gaseous exchange (CO2 and O2) between the intercellular spaces of plant cell and the outer air takes place through stomata during photosynthesis
- During respiration, plants receive O2 and release CO2 through stomata.