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The dance of water and light: Why are guard cells so critical to plant survival?
In the life system of plants, guard cells play a vital role. These specialized cells are located on the epidermis of leaves and other organs and are responsible for controlling gas exchange, especially under the influence of water and light. The operation of guard cells not only affects the survival of the plant, but also affects the balance of the entire ecosystem.
Guard cells consist of a pair of cells with a central stomata forming, and the size of these stomata changes with the availability of water. When there is enough water, the guard cells swell and open the stomata, otherwise they close.
Function of guard cells
Guard cells are cells around each stomata that regulate the rate of evapotranspiration by opening and closing the stomata. Under strong light, the operation of guard cells is stimulated, causing the stomata to open, allowing carbon dioxide to enter and oxygen to escape. This process is essential for photosynthesis.
Under the stimulation of light, the change in water concentration inside the guard cells causes the cells to expand and open the stomata. The dynamics of this process involve the interaction of proton pumps and sodium-potassium channels.
Water loss and water use efficiency
When faced with environmental issues such as drought and salt stress, plants must resist water loss through a variety of mechanisms. The plant hormone abscisic acid (ABA) plays an important role in this process. When moisture is limited in the environment, the production of ABA prompts guard cells to close the stomata, thereby reducing the plant's evaporative losses.
Research has found that ABA promotes the release of negative ions and potassium ions. This process causes changes in membrane potential of guard cells, quickly starting cell contraction, thereby closing the stomata.
Ion entry and exit and signal transduction
The entry and exit of ions in guard cells is crucial for the opening and closing of stomata. The entry and release of potassium ions (K+) promote and inhibit the opening of stomata respectively. In addition to potassium ions, negative ions such as chloride ions also play an important role in stomata closure.
Guard cells sense environmental changes, such as light, humidity and CO2 concentration, and adjust their physiological responses to adapt to the surrounding environment.
Guard cells in cell development
The development of guard cells is equally important. These specialized cells differentiate from "guard mother cells" and the density of stomata on the leaf surface is affected by a variety of environmental factors, including the concentration of carbon dioxide in the atmosphere. As CO2 concentration increases, the number of stomata of some plants decreases significantly. This adjustment mechanism remains to be further explored.
Using a microscope to directly observe the leaf epidermis, the development process of guard cells can be clearly studied, and a variety of control proteins involved in the differentiation of guard cells can be identified.
In general, guard cells are not only vital to the survival of the plant itself by regulating water and gas exchange, but also directly affect the water cycle and climate balance of the ecosystem. With a better understanding of these cellular mechanisms, crops that are more drought-resistant and water-use efficient may be developed in the future. However, have we fully realized the importance of guard cells in facing the challenge of climate change?
