Under which condition is water a limiting factor for photosynthesis?

Water becomes a limiting factor for photosynthesis primarily during drought conditions. In normal situations, plants take up water through their roots, which is essential for photosynthesis, as it is a key reactant in the process. During droughts, the availability of water decreases significantly, leading to reduced plant hydration. This can cause plants to close their stomata (tiny openings on leaves) to minimize water loss, which in turn limits the uptake of carbon dioxide—a necessary component for photosynthesis. When stomata are closed, the process of photosynthesis is hindered, resulting in lower rates of glucose production.

In contrast, during regular rain cycles, there is usually sufficient water available for plants to carry out photosynthesis effectively. Optimal temperature conditions support physiological processes in plants that enhance photosynthesis, while higher light intensities typically increase the rate of photosynthesis, assuming that other factors (like water) are not limiting. Therefore, drought is the specific condition under which water directly limits the ability of plants to perform photosynthesis.