Question

Describe the structure of stomata and explain its function and how they open and close

Answer 1

Stomata are tiny pores in plant tissue that allow for gas exchange. Stomata are typically found in plant leaves but can also be found in some stems. Specialized cells known as guard cells surround stomata and function to open and close stomatal pores.

Epidermis Cll Chloroplast -Stomatal Pore Sap Vacuole Thick Inner Wall Subsidiary Cells- Thin Outer Wall Nucleus Guard Cells

Stomata allow a plant to take in carbon dioxide, which is needed for photosynthesis. They also help to reduce water loss by closing when conditions are hot or dry. Stomata look like tiny mouths which open and close as they assist in transpiration.

The two main functions of stomata are to allow for the uptake of carbon dioxide and to limit the loss of water due to evaporation. In many plants, stomata remain open during the day and closed at night. Stomata are open during the day because this is when photosynthesis typically occurs. In photosynthesis, plants use carbon dioxide, water, and sunlight to produce glucose, water, and oxygen. Glucose is used as a food source, while oxygen and water vapor escape through open stomata into the surrounding environment. Carbon dioxide needed for photosynthesis is obtained through open plant stomata. At night, when sunlight is no longer available and photosynthesis is not occurring, stomata close. This closure prevents water from escaping through open pores.

The opening and closing of stomata are regulated by factors such as light, plant carbon dioxide levels, and changes in environmental conditions. Humidity is an example of an environmental condition that regulates the opening or closing of stomata. When humidity conditions are optimal, stomata are open. Should humidity levels in the air around plant leaves decrease due to increased temperatures or windy conditions, more water vapor would diffuse from the plant into the air. Under such conditions, plants must close their stomata to prevent excess water loss.

Stomata open and close as a result of diffusion. Under hot and dry conditions, when water loss due to evaporation is high, stomata must close to prevent dehydration. Guard cells actively pump potassium ions (K⁺) out of the guard cells and into surrounding cells. This causes water in the enlarged guard cells to move osmotically from an area of low solute concentration (guard cells) to an area of high solute concentration (surrounding cells). The loss of water in the guard cells causes them to shrink. This shrinkage closes the stomatal pore.