Saguaro Gas Exchange: CAM Photosynthesis, Night Stomatal Opening

CAM Mechanism

Saguaro uses Crassulacean Acid Metabolism:

1. Night: Stomata open → CO₂ enters → stored as malic acid.
2. Day: Stomata closed → malic acid decarboxylated → CO₂ for Calvin cycle.

Structures

• Stomata on stem epidermis (fewer than leaves).
• Thick cuticle, sunken stomata reduce water loss.
• Chlorophyll in stem cortex (photosynthetic stem).

Homework note: Library research builds deeper understanding.