The control of stomata by water balance

Summary It is clear that stomata play a critical role in regulating water loss from terrestrial vegetation. What is not clear is how this regulation is achieved. Stomata appear to respond to perturbations of many aspects of the soil–plant–atmosphere hydraulic continuum, but there is little agreement regarding the mechanism (or mechanisms) by which stomata sense such perturbations. This review discusses feedback and feedforward mechanisms by which hydraulic perturbations are putatively transduced into stomatal movements, in relation to generic empirical features of those responses. It is argued that a metabolically mediated feedback response of stomatal guard cells to the water status in their immediate…