How do CAM plants adapt to arid conditions for photosynthesis?

CAM plants adapt to arid conditions for photosynthesis by opening their stomata at night to minimise water loss.

Crassulacean Acid Metabolism (CAM) is a photosynthetic adaptation employed by several plants to survive in arid conditions. This unique process allows plants to open their stomata (tiny pores on the surface of leaves) during the night when the temperature is cooler and humidity is higher, thus reducing water loss through transpiration. During this time, they take in carbon dioxide and store it as malic acid in their vacuoles.

During the day, when the stomata are closed to prevent water loss, the stored malic acid is converted back into carbon dioxide within the cells. This carbon dioxide is then used in the Calvin cycle to produce sugars, just like in the normal photosynthesis process. This adaptation allows CAM plants to carry out photosynthesis during the day without losing precious water through open stomata.

The CAM process is an example of a trade-off between water conservation and growth rate. While it allows plants to survive in harsh, arid conditions, it is a slower process than regular photosynthesis because the carbon dioxide is stored and used later rather than being used immediately. This means that CAM plants generally grow more slowly than other plants.

However, the ability to switch between CAM photosynthesis and regular photosynthesis depending on environmental conditions gives these plants a significant survival advantage in changing climates. This flexibility is particularly important in desert environments where water availability can vary greatly.

In summary, CAM plants have evolved a unique way to carry out photosynthesis that allows them to conserve water in arid conditions. By opening their stomata at night to take in carbon dioxide and closing them during the day to prevent water loss, they can continue to photosynthesise and grow even in harsh desert environments.