Question: what causes reversed stomatal opening in some xeropyites

Jacinta Nzilani answered on 17 Jul 2025:

Hey,
🌵 Why Xerophytes Reverse Their Stomatal Opening.

Xerophytes are plants adapted to dry environments -they use a reversed stomatal rhythm: their stomata are closed during the hot day and open at night.

🔬 Scientific Reasons (Based on CAM Photosynthesis).

These plants perform Crassulacean Acid Metabolism (CAM): they open stomata at night to absorb CO₂, which is stored as malic acid in vacuoles. During the day, stomata remain closed to conserve water, while the stored CO₂ is used in photosynthesis.

Opening stomata at night minimizes water loss, since the nighttime temperatures are cooler and the humidity is higher, reducing evapotranspiration.