Cactus Transpiration: Nighttime Stomatal Opening

CAM Photosynthesis

Cacti transpire like other plants, but stomata open at night (Crassulacean Acid Metabolism).

Process

1. Night: Stomata open → CO₂ enters → stored as malic acid.
2. Day: Stomata closed → malic acid decarboxylated → CO₂ for Calvin cycle.
3. Result: Water loss minimized (cooler, humid night air).

Significance

Allows survival in extreme aridity. Transpiration ratio (water lost per CO₂ fixed) is 10× lower than C3 plants.