A plant that utilizes the Crassulacean acid metabolism (CAM) as an adaptation for arid conditions. CO2 entering the stomata during the night is converted into organic acids, which release CO2 for the Calvin Cycle during the day, when the stomata are closed.
Cam plants utilize an elaborate carbon fixation pathway in a way that the stomata are open at night to permit entry of CO2 to be fixed and stored as a four-carbon acid (i.e. malate).Then, during the day the CO2 is released for use in the Calvin cycle. In this way, the rubisco is provided with high concentration of CO2 while the stomata are closed during the hottest and driest part of the day to prevent the excessive loss of water. CAM plants are therefore highly adapted to arid conditions.