Guard cell意思

"Guard cell" is a term used in botany to refer to a specialized type of cell found in the epidermis of plant leaves. These cells are an important part of the plant's ability to regulate gas exchange, particularly the intake of carbon dioxide (CO2) for photosynthesis and the release of oxygen (O2) during the day.

Guard cells are located at the ends of the stomata, which are tiny pores in the surface of the leaf. Each stoma is flanked by two guard cells that control the opening and closing of the pore. When the guard cells become turgid (filled with water), they bend and the stoma opens, allowing gases to enter and exit the leaf. When the guard cells lose water and become flaccid, they straighten out, and the stoma closes.

The opening and closing of stomata are controlled by various environmental factors, such as light intensity, humidity, and carbon dioxide concentration. For example, when a plant is exposed to bright light, the guard cells may absorb potassium ions (K+) and become turgid, causing the stomata to open so that the plant can take in CO2 for photosynthesis. In low light or when the plant is stressed by drought, the guard cells may lose K+ and become flaccid, closing the stomata to reduce water loss through transpiration.

Guard cells play a crucial role in the plant's water balance and its ability to photosynthesize efficiently. They are also involved in the regulation of plant transpiration and the exchange of gases between the plant and the atmosphere.