Potometer: Ganong's

For the demonstration of transpiration rates and rates of water absorption by a cut shoot under various external conditions.

The whole apparatus is filled with water and a plant shoot is sealed into a stopper which fits the end tube. The open end of the capillary tube, which is graduated in millimeters, is placed into a beaker of water.  An air bubble is generator by dipping the graduated tube out of and back into a beaker of water.

The position of the air bubble may easily be adjusted by opening the glass stopcock to admit water from the reservoir.

The air bubble can be made more visually obvious using coloured water.

• Apparatus is mounted on a wooden base by clips.

Different environmental factors can be investigated.  For example, by adding vaseline to the upper surface of the leaves, or by placing the plant inside a plastic bag.