How does CO2 affect limiting factor for photosynthesis?
Several ways. Plants have to compromise between water loss in hot climates with intense sunlight and freely exchanging gases because they do not have separate pathways for water movement and gas exchange with the atmosphere. Both water and CO2 are rate-limiting factors for photosynthesis to proceed and both pass through the stomata. To get enough CO2 for photosynthesis, too much water may be lost to transpiration, and the plant injured by desiccation. The plant must shut off the stomata to prevent desiccation but then it cannot photosynthesize for the lack of CO2 (except C4 & CAM plants that have a facilitated diffusion of CO2 into storage). Leaf photorespiration increases sharply above 30 C because dissolved CO2 concentration is reduced. Increasing temperature leads to less carbon dioxide solubility in cell cytoplasm than oxygen. Since the O2 is in solution it binds RuBisCo taking the enzyme out of the photosynthetic process. As a result photorespiration increases and the net photosyn
