In the context of the water cycle, what does a potometer measure in a laboratory?

Correct answer: Rate of water uptake by a plant shoot, used as an estimate of transpiration

Correct answer: B. A potometer is an apparatus used mainly to estimate the rate at which a cut plant shoot takes up water. In a typical setup, the shoot is connected to a water-filled tube containing a small air bubble. As water is lost from the leaves by transpiration, the shoot usually takes up water, causing the bubble to move. The distance moved per unit time provides an estimate of water uptake and therefore an indirect estimate of transpiration. It is not a direct measurement of all water vapour leaving the plant, because some absorbed water may be used in metabolism or maintained in tissues. A measures evaporation from a surface, C concerns movement through soil, and D is measured with humidity instruments. Memory cue: potometer follows the plant’s water uptake to estimate transpiration.