What is the main storage mechanism for CO2 in CAM plants?

CAM (Crassulacean Acid Metabolism) plants have a unique adaptation that allows them to minimize water loss in arid environments, and a key part of this adaptation involves the storage and use of carbon dioxide. During the cooler and more humid nighttime hours, these plants take in CO2 from the atmosphere and store it in the form of organic acids, primarily malate.

The process starts when the stomata, the small openings on leaves, open at night to allow CO2 to enter while the temperatures are lower and the humidity is higher, reducing water loss. The incoming CO2 is then fixed into a four-carbon compound, mainly malate. This malate is stored in vacuoles until daytime.

When daylight arrives, the stomata are closed to conserve water. The stored malate is subsequently decarboxylated to release CO2 internally, which is then utilized in the Calvin cycle for photosynthesis while the stomata remain closed. This efficient method of CO2 storage and usage allows CAM plants to thrive in environments where water conservation is critical.

Thus, the main storage mechanism for CO2 in CAM plants occurs through its conversion to malate at night, enabling the plant to effectively utilize carbon for photosynthesis during the day