Question

What is the role played by the air bubble in a Ganong's Potometer?

Answer 1

The air bubble in Ganong's potometer is to mark the progress of transpiration and absorption of water by the freshly cut leafy twig which must be devoid of any roots.

Answer 2

A photometer is a device which is used to measure the rate of water uptake by the plant. The water taken up by the plant is used in photosynthesis and transpiration.

The usage of bubble in ganong’s photometer is to determine how much water has been taken up by the roots of the plants. How far the bubble goes or how much distance it covers tells the rate of uptake of water by the plant.