What is the main function of guard cells in plants?

Guard cells are specialized cells that flank the stomata on the surface of plant leaves and stems. Their primary function is to regulate gas exchange between the internal tissues of the plant and the external environment. By controlling the opening and closing of the stomata, guard cells manage the intake of carbon dioxide for photosynthesis and limit the loss of water vapor during transpiration.

When conditions are favorable for photosynthesis, guard cells take in water and swell, causing the stomata to open. Conversely, when the plant is losing too much water or when it is dark, guard cells lose water and become flaccid, resulting in the closing of the stomata. This regulation is crucial for maintaining homeostasis within the plant, balancing the need for gas exchange with the need to conserve water. Thus, the role of guard cells is essential for the plant’s overall health and efficiency in photosynthesis.