Measuring Cactus Transpiration: Experimental Design for Student Project

Feasible Method: Humidity Chamber

1. Enclose each plant (cactus, rose) in separate clear, sealed chambers (large plastic bins).
2. Place humidity/temperature data loggers inside.
3. Record RH rise over set periods (day vs. night).
4. Control: empty chamber.

Key Cactus Physiology

CAM photosynthesis: stomata open at night → transpiration occurs mainly in dark. Rose (C3) transpires by day. Compare night cactus RH rise vs. day rose RH rise.

Simpler Alternative

Gravimetric: weigh potted plants at same time daily. Weight loss = transpiration. Control for soil evaporation (cover soil with foil).