Leaves may have 1,000-60,000 pores per square centimeter. When open, stomata are 10–40 µm in length and 3–12 µm in width. Different parts of stomata are-
1. Stomata pore: There is a special type of pore in the center of the stomata. This is called stomatal pore. Different types of gaseous substances are exchanged through it.
2. Guard cells: Stomata are covered by two crescent-shaped cells. It is called Rakshikosh. Each guard cell contains cytoplasm, chloroplasts, mitochondria, cytoplasm and a large nucleus. The guard cell has two walls. Outer wall and inner wall. The inner wall is thick and inelastic. But the outer wall is thin, semipermeable and elastic. Guard cells are covered by 2-4 epidermal cells. It controls the opening and closing of stomata.
3. Supporting cells: There are some special types of parenchyma cells surrounding the stoma. These are called accessory cells. Each stomata with accessory cells is called a stomatal complex. Some plants do not have accessory cells. Like- Pumpkin, Cucumber, Orchid etc.
4. Air chamber : There is a large air-filled cavity below the stomata. It is called substomatal cavity. This chamber is also known as air cavity or respiratory cavity.
The leaf pores are hidden deep in the skin. This is called hidden or submerged stomata. The stomata are open during the day and closed at night. However, the stomata of Patharkuchi plants are closed during the day and open during the night. The plant’s stomata are fully open from 10-11 am and 1-3 pm.