many succulent xerophytes employ the crassulacean acid metabolism or better known as cam photosynthesis. it is also dubbed the "dark" carboxylation mechanism because plants in arid regions collect carbon dioxide at night when the stomata open, and store the gases to be used for photosynthesis in the presence of light during the day. although most xerophytes are quite small, this mechanism allows a positive carbon balance in the plants to sustain life and growth. prime examples of plants employing the cam mechanism are the pineapple, "agave americana", and "aeonium haworthii".