C3 and C4 plants and CAM

CO₂ concentration and water conservation Land plants have to open their stomata to admit CO₂. This means water loss is inevitable while photosynthesis occurs. Atmospheric concentrations of CO₂ do not saturate Rubisco and it therefore functions at less than its maximal rate. C4 photosynthesis and crassulacean acid metabolism (CAM) are two adaptations which decrease water loss.