What is a potometer?

A potometer is an apparatus used in plant physiology experiments to measure the rate of water uptake by a plant. Since most of the water absorbed by a plant is lost through transpiration, a potometer indirectly provides a way to estimate the rate of transpiration.

The apparatus usually consists of a cut plant shoot connected to a glass tube filled with water, with one end of the tube dipping into a reservoir. A small air bubble is introduced into the capillary tube, and as the plant transpires, it absorbs water from the tube, causing the bubble to move. The distance moved by the bubble over a certain time interval is recorded, which gives a measure of the rate of water uptake.

There are different types of potometers, such as the simple potometer, Darwin’s potometer, and the commonly used Ganong’s potometer. Each design works on the same principle but may vary in construction and accuracy.

It is important to note that the potometer does not measure transpiration directly, but water uptake, which is assumed to be nearly equal to the amount of water lost by transpiration. Environmental factors like light, temperature, humidity, and wind can affect readings.