Cacti use the process of crassulacean acid metabolism (CAM) to minimize water loss. This adaptation allows cacti to open their stomata at night instead of during the hot day, reducing water evaporation. During the night, they absorb carbon dioxide and store it as malate, which is then utilized for photosynthesis during the day when the stomata remain closed. This efficient water-conserving mechanism enables cacti to survive in arid environments while still performing photosynthesis.