Which factor influences the rate of carbon fixation in CAM plants?

The rate of carbon fixation in CAM (Crassulacean Acid Metabolism) plants is primarily influenced by humidity and water availability due to their unique adaptations to arid environments. CAM plants perform carbon fixation during the night when temperatures are cooler and humidity is typically higher. This adaptation helps minimize water loss through transpiration. At night, they open their stomata to take in carbon dioxide, which is then stored as malate. During the day, the stomata close to conserve water, and the stored carbon dioxide is utilized for photosynthesis. Therefore, both humidity and water availability directly impact the efficiency of this process, as high humidity facilitates better gas exchange and reduces the need for water use.

Soil nutrient availability, daylight duration, and nighttime temperature can have some effects on plant growth and overall health, but the specialized adaptation of CAM plants particularly links the effectiveness of carbon fixation to the environmental factors of humidity and water.