Building & Using a Potometer: Measuring My Plant’s Thirst - kssm form 5 biology

 

Understanding theory is one thing—quantifying it is another. I built a simple potometer to measure transpiration rate:

• Cut a leafy shoot under water to prevent air embolisms.
• Fit it airtight into a graduated glass tube filled with water.
• Record how far an air bubble moves in a set time.

Plotting distance vs. time gave me a clear rate of water uptake, which closely mirrors transpiration rate under constant conditions.

Sample SPM Question

“Design an experiment using a potometer to compare transpiration rates at different light intensities.”

I described:

1. Keeping temperature and humidity constant.
2. Varying light intensity with a lamp.
3. Repeating each intensity three times and calculating mean bubble movement.