CAM plants include most succulents, such as cacti and agaves, as well as some orchids and bromeliads. CAM is an acronym for crassulacean acid metabolism, and it refers to a specific type of photosynthesis generally used by plants and vegetation growing in hot and arid climates.
CAM photosynthesis was first discovered in the plant family Crassulaceae. Plants that perform this type of photosynthesis, like other photosynthesizers, obtain energy from the sun. However, instead of combining sunlight with water to produce glucose, an instant source of energy, CAM plants combine sunlight with carbon dioxide. The carbon dioxide is stored in acid form; some supplies are used immediately to complete the process of photosynthesis, while the remaining portion is stored for future use.
CAM plants also complete photosynthesis at night; their stomata open at night, but close during the day to conserve water and energy. During the day, cacti and other CAM plants break down stored acid, which in turn releases carbon dioxide. These plants are adept at making efficient use of water under arid conditions. This is facilitated by their stomata, which open in the dark, when temperatures are lower and when wind speeds are minimal. The CAM process of photosynthesis helps desert-dwelling plants survive dry spells and recover more quickly when water becomes available again.