Which nutrient regulates stomatal openings in plants?

The correct nutrient that regulates stomatal openings in plants is potassium. Potassium plays a crucial role in the function of guard cells, which surround the stomata (tiny openings on the surface of leaves). When potassium ions are actively transported into guard cells, it causes water to follow by osmosis. This inflow of water enlarges the guard cells, leading to the opening of the stomata. Conversely, when potassium is withdrawn from the guard cells, the cells lose water and become flaccid, resulting in the closing of the stomata. This process is vital for regulating gas exchange and transpiration in plants, allowing them to maintain homeostasis in response to environmental conditions.

Other nutrients listed, while important for various physiological functions and overall plant health, do not directly regulate stomatal movements in the same manner as potassium. Calcium is essential for cell wall structure and stability. Magnesium is crucial for chlorophyll production and plays a role in photosynthesis, while nitrogen is primarily involved in amino acid and protein synthesis. However, none of these nutrients have the direct impact on stomatal regulation that potassium does.