Temperature

Both light and dark reactions are affected by temperature, although the light reaction is affected to a lesser extent as compared to dark reaction.
The dark reactions involve a lot of enzymatic reactions and is temperature controlled. The C4 plants show enhanced photosynthesis at higher temperatures while C3 plants have a much lower temperature optimum. Different plants show different temperature optimums for photosynthesis depending on there habitat. Plants living in tropical habitats have a higher temperature optimum than the plants adapted to temperate climates. Water deficit Water does not affect the photosynthesis process directly. Water stress causes stomatal closure thereby reducing the CO2 availability. Moreover, the surface area of leaves and the metabolic activity of the leaves is reduced as the leaves wilt in water deficit conditions. Soil water Water also helps to maintain the temperature required for photosynthesis, it helps in the uptake of minerals and ions from the soil and helps in stomatal opening and closing as well. Only 1 percent of the soil water is used by the plants in processes such as photolysis of water and to carry out biochemical reactions.