Question

Stomata of CAM plants

• A. Are always open
• B. Open during the day and close at night
• C. Open during the night and close during the day
• D. Never open

Answer 1

Answer: (C)

Stomata of most plants open at sunrise and close in darkness to allow the entry of CO₂ needed for photosynthesis during the daytime. Certain succulents that are native to hot, dry conditions (e.g., cacti, Kalanchoe, and Bryophyllum) act in an opposite manner. They open their stomata at night, fix carbon dioxide into organic acids in the dark, and close their stomata during the day. This is an appropriate way to absorb CO₂ through open stomata at night, when transpiration stress is low, and conserve water during the heat of the day. These plants show Crassulacean Acid Metabolism (CAM).