Which cells are responsible for controlling the size of the stomata?

Guard cells are specialized cells that control the size of the stomata, which are small openings on the surface of leaves and stems. These cells surround each stoma and can change shape in response to environmental conditions. When guard cells take in water, they swell and curve, causing the stomatal pore to open; conversely, when they lose water, they become flaccid and close the pore. This regulation of stomatal opening and closing is crucial for gas exchange, allowing carbon dioxide to enter for photosynthesis while minimizing water loss through transpiration. This dynamic control enables plants to adapt to changes in light, humidity, and overall water availability.