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Light-Dependent Stomatal Opening
Light-dependent stomatal opening occurs in many species and under many different conditions. Light is a major stimulus involved in stomatal conductance, and has two key elements that are involved in the process: the stomatal response to blue light, and photosynthesis in the guard cell's chloroplast. The stomata open when there is an increase in light, and they close when there is a decrease in light. This is because the blue light activates a receptor on the guard cell membrane which induces the pumping of protons of of the cells, which creates an electrochemical gradient. This causes free floating potassium and other ions to enter the guard cells via a channel. The increase in solutes within the guard cells leads to a decrease in the osmotic potential of the cells, causing water to flood in, the guard cell's to become enlarged, and therefore open.The second key element involved in light-dependent stomatal opening is the photosynthesis in the guard cell's chloroplast. This event also increases the amount of solutes within the guard cell. Carbon Dioxide enters the chloroplasts which increases the amount of photosynthesis. This increases the amount of solutes that are being produced by the chloroplast which are then released into the cytosol of the guard cell. Again, this causes a decrease in osmotic potential, water floods into the cells, the cells swell up with water, and the stomate is opened.

Recent studies have looked at the stomatal conductance of fast growing tree species to identify the water use of various species. Through their research it was concluded that the predawn water potential of the leaf remained consistent throughout the months while the midday water potential of the leaf showed a variation due to the seasons. For example, canopy stomatal conductance had a higher water potential in July than in October. The studies conducted for this experiment determined that the stomatal conductance allowed for a constant water use per unit leaf area. Other studies have explored the relationship between drought stress and stomatal conductance. Through these experiments, researchers have found that a drought resistant plant regulates it's transpiration rate via stomatal conductance. This minimizes water loss and allows the plant to survive under low water conditions.