Explain the Mechanism of Opening and Closing of Stomata

Answer: Guard cells are specialized plant cells that regulate gas exchange in the epidermis of leaves, stems, and other organs. They are produced in pairs, with a stomatal pore-forming the gap between them. When water is abundant and the guard cells are turgid, the stomatal pores are the largest; when water is scarce and the guard cells become flaccid, the stomatal pores close. The diffusion of carbon dioxide (CO₂) from the air into the mesophyll tissues is required for photosynthesis.

The small openings found on the leaf epidermis are known as stomata. Stomata can be seen beneath the light microscope. Some plants have stomata on their stems and other parts.

Stomatal Structure

• Each stoma has two guard cells surrounding it

• Chloroplasts are found in the guards, which are kidney-shaped

• In each stoma, there is a respiratory chamber

The turgidity of the guard cells determines when the stomata close and open. On the side facing the stoma, each guard cell has a thicker wall, while the opposite side has a thin wall. Chloroplasts are found in guard cells. The osmotic pressure of the contents of the guard cells rises as a result of glucose synthesis during photosynthesis and other chemical changes, and they absorb more water from neighboring cells, becoming turgid. The guard cells become more arched outwards as a result of turgor, and the aperture between them widens, thus opening.

The stoma is a tube that connects the intestines to the stomach The guard cells become flaccid at night or when there is a lack of water in the leaf, and their inner rigid walls become straight, closing the stomatal aperture.

The sugar present in guard cells converts to starch in the absence of light. Because the starch is insoluble, the guard cells have a lower concentration than the neighboring cells and the neighboring cells osmosis the water out of the guard cells, causing them to become flaccid and their stomata to close.