Root Pressure and Leaf Water Potential

Abstract

Measurements with thermocouple psychrometers were made of the water potentials of leaves from sunflower and pepper plants which had stood overnight in the dark in nutrient solutions containing carbowax. Similar measurements on the solutions showed that they had lower water potentials than the leaves, although the plants were measurably transpiring. Evidence that root pressure plays a part in this inversion of water potential gradient is presented.