Measurement of Stem Water Potential of Young Plants Using a Hygrometer Attached to the Stem

Abstract

A simple method was developed for the continuous non-destructive measurement of plant stem water potential. It consists of exposing a small section of stem vascular tissue and attaching to it a standard commercially available dewpoint hygrometer. Excellent agreement was found between water potential determined by this method, and that measured with a pressure-chamber on leaves covered with aluminium foil. Stem water potentials responded within minutes to changes in radiation and transpiration. Resistance to water uptake was found to be independent of the rate of transpiration.