Which process primarily occurs during the night in CAM photosynthesis?

In CAM (Crassulacean Acid Metabolism) photosynthesis, the process that primarily occurs during the night is the dark reactions, which involve the fixation of carbon dioxide to synthesize carbohydrates. This adaptation allows plants, such as succulents and some cacti, to conserve water in arid conditions.

During the night, CAM plants open their stomata to allow CO2 to enter the leaf. The CO2 is then converted into malate and stored in vacuoles. This process minimizes water loss, as stomata are closed during the day to reduce transpiration. When daylight arrives, the stored malate is decarboxylated, releasing CO2 to the Calvin cycle, where it can be used to produce sugars and other carbohydrates in the presence of light.

Focusing on the other options, the light reactions of photosynthesis and water splitting to create oxygen occur during the day when light is available, as these processes require sunlight. ATP production via cyclic photophosphorylation is also part of the light-dependent reactions, which take place in the presence of light. Thus, the synthesis of carbohydrates from the fixed carbon during the night is a key characteristic of CAM plants, allowing them to adapt to their environments efficiently.