Function of Guard Cells of Stomata

Guard cells are specialized cells located in the epidermis of leaves and stems of plants. They have an important function in regulating the opening and closing of stomata.

Regulation of Stomatal Opening and Closing

The main function of guard cells is to regulate the opening and closing of stomata. Stomata are small pores on the surface of leaves and stems that allow for gas exchange between the plant and the environment. When the plant needs to take in carbon dioxide for photosynthesis, the stomata open, and when it needs to conserve water, the stomata close.

Structure of Guard Cells

Guard cells are kidney-shaped cells that are usually found in pairs surrounding the stomata. They have a thickened inner wall and a thinner outer wall, and they are able to change shape to control the size of the stomatal opening.

Mechanism of Stomatal Opening and Closing

The opening and closing of stomata is controlled by the turgor pressure of the guard cells. When the guard cells take in water, they become turgid and swell, causing the stomatal opening to widen. Conversely, when the guard cells lose water, they become flaccid and shrink, causing the stomatal opening to narrow.

Factors Affecting Stomatal Opening and Closing

The opening and closing of stomata is affected by a number of environmental and internal factors, including:

- Light: Stomata tend to open during the day and close at night.
- Carbon dioxide concentration: When carbon dioxide levels are low, stomata tend to open to allow for more carbon dioxide uptake.
- Temperature: Stomata tend to open in response to high temperatures to release excess water vapor.
- Water availability: Stomata tend to close when water is scarce to conserve water.

Conclusion

In summary, guard cells have an important function in regulating the opening and closing of stomata to control gas exchange and water loss in plants. They are able to change shape in response to environmental and internal cues to maintain the plant's water balance and ensure optimal photosynthesis.

Each pair of guard cells and the regulated pore they enclose, known as a stoma or stomate, provides a conduit for atmospheric photosynthetic gas exchange (CO2 uptake and O2 release) and transpirational release of water (H2O) in terrestrial plants, in addition to defense against pathogenic invasion.