Soil Water Status Affects the Stomata1

Abstract

Wheat and sunflower were grown in pots that could be enclosed in a pressure chamber, with the shoot in a cuvette. Applying an appropriate pneumatic pressure to the roots enabled the leaves to be kept fully turgid despite any drying of the soil. The leaf conductance of plants was followed while the soil dried. Remarkably, this conductance fell with falling soil water content no matter whether the leaves were kept fully turgid or not. It is concluded that the roots sensed the drying of the soil and sent a message to the leaves which induced stomatal closure.