Potometer Ganong's

This Ganong's potometer on a wooden base is a lab apparatus for measuring the rate of transpiration in plants by tracking how much water they take up. It's a standard tool in school biology labs for showing how environmental factors like light, wind and humidity affect a plant's water loss.

Core Components and Design

• Glassware: A graduated, narrow-bore capillary tube (typically 1mm bore) bent at a right angle.
• Reservoir: A vertical funnel or limb with a glass or PTFE stopcock for resetting the air bubble and refilling the system.
• Shoot holder: A wide-mouthed glass cylinder or end tube where a freshly cut leafy shoot is sealed in with a rubber stopper.
• Base: The whole unit is mounted on a polished, varnished wooden base (about 320 x 80mm) with spring clips to keep it steady during experiments.

How It Works

1. Setup: Fill the apparatus with water and seal a cut plant shoot into the end tube.
2. Add a bubble: Introduce a single air bubble into the graduated capillary tube.
3. Measure: As the plant transpires, it pulls water from the tube and the bubble moves. The distance the bubble travels in a set time shows the rate of water uptake.
4. Reset: Open the stopcock to release water from the reservoir, pushing the bubble back to the start for a new trial.