What unique metabolic adaptation do CAM plants have?

CAM plants, or Crassulacean Acid Metabolism plants, have developed a unique adaptation that allows them to thrive in arid conditions. One of their primary metabolic strategies is to fix carbon dioxide at night when temperatures are cooler and humidity is generally higher. This reduces water loss compared to daytime fixation, which would occur when stomata are open.

During the night, CAM plants take in CO2 and convert it into organic acids, like malate, which are stored within the plant's vacuoles. During the day, when the stomata are closed to minimize water loss, these organic acids are broken down to release CO2 for use in the Calvin cycle, allowing the plant to continue photosynthesis without losing excessive water. This adaptation is especially beneficial in environments where water is scarce, enabling CAM plants to maintain their metabolic processes while conserving moisture.

The other concepts, such as separating carbon fixation and the Calvin cycle in different cells or relying solely on Rubisco for carbon fixation, do not accurately represent the unique adaptations of CAM plants. Additionally, while some photosynthetic processes can occur at night in other types of plants, CAM specifically utilizes night-time CO2 fixation in its unique metabolic pathway.