All plants require sunlight, carbon dioxide and water to perform photosynthesis. CAM plants convert carbon dioxide to an acid and store it in their leaves before photosynthesis begins. (See reference 1)
CAM plants take in carbon dioxide during the night through pores in their leaves. During the day, the pores close and the stored carbon dioxide is used for photosynthesis. (See reference 1)
Desert plants or plants that live in arid environments are vulnerable to desiccation. CAM photosynthesis allows plants to keep pores closed during the day, when the sun and wind would otherwise cause plants to lose the most water. (See reference 1)
The CAM process allows plants to complete photosynthesis when environmental conditions are not optimal, which probably lent significant evolutionary advantages to plants with the CAM pathway under arid conditions.
Plant physiologists believe that CAM photosynthesis has evolved independently many times, as more than 20 different plant families exhibit this type of photosynthesis. Cacti, orchids and bromeliads are some of the types of plants that show CAM photosynthesis. (See reference 2)