Abstract
Pretreatment of soybean (Glycine max L. var Ransom) root systems with abscisic acid (ABA) ameliorates the deleterious effect of low temperatures on root hydraulic conductance. ABA treatment of root systems subsequently chilled to 10 degrees C with shoots at 25 degrees C resulted in higher leaf water potentials and lower stomatal resistances. If the root systems are left at 25 degrees C, ABA causes stomatal closure. Membrane alterations are suggested as a mechanism for the ABA action in plant response to chilling stress.