Malic Acid Build Up & Release
CAM plants or those plant species such as bromeliads, orchids, euphorbias and dracaenas use a secondary survival process called crassulacean acid metabolism (CAM) to survive very dry growing conditions like those found in the desert. This is an additional nutrient and water management process beyond basic carbon dioxide fixing which all plants perform. Malic acid builds up in plants overnight through the standard carbon fixing process and is cannibalized by the plant during the daylight hours. CAM plants capture the carbon dioxide given off in this cannibalization process to fuel the secondary life support process.
Open & Closed Cycling Stomata
Non-CAM plant cells or stomata open and close throughout the day and night to absorb carbon dioxide and release oxygen. CAM process plants only open to absorb carbon dioxide at night when temperatures in their arid habitats are lower. They close off their cells during the day to prevent moisture loss in the transfer when the temperatures are hotter. This night-only process lets CAM plants conserve more moisture.
The driest desert conditions can induce some plants to lock up their stomata preventing them from ever opening. This creates a closed system where water does not evaporate and the carbon dioxide is recycled inside the plant cells. This process is called CAM idling and keeps plant cells alive in stasis during extreme drought stress but is not dynamic enough to support cell and therefore plant growth.