The co-regulatory interaction of transpiration and water potential, and implications for stomatal conductance models

Abstract

Leaf water potential decreases with increasing transpiration rate according to an analogue of Ohms law, while transpiration rate decreases with decreasing leaf water potential in the framework of stomatal control. This interaction is not accommodated in present-day models of stomatal conductance. We formally derive the equilibrium between these two counteracting processes for steady-state water conditions. We show that the mechanism considered causes an attenuation of the immediate effect of atmospheric variables on transpiration, which can improve existing models of stomatal conductance that presume noninterdependent variables. Parameters from European beech (Fagus sylvatica L.) are used to illustrate the results.