Resistance to Water Transport in Plants—a Misconception?

Abstract

PROFESSOR LEVITT¹ argues that the chief resistance to water transfer through the soil-plant-atmosphere continuum is in the liquid path through the plant, and not in the gaseous path from plant to atmosphere as concluded by Gradmann² and van den Honert³. The basis of his argument is that while water potentials are appropriate to transfer of the liquid through the plant, vapour pressures should be used in the Ohm's law analogue of the flow from plant to atmosphere, because gas diffuses in response to a vapour pressure gradient.