Exogenous catalase and ascorbate modify the effects of abscisic acid (ABA) on root hydraulic properties in Phaseolus vulgaris L. Plants

Abscisic acid (ABA) modifies the hydraulic properties of roots by increasing root water flux (J(v)). The role of reactive oxygen species (ROS) in this ABA-induced process was evaluated. At the same time, some antioxidant enzyme activities in root tissues were measured. Phaseolus vulgaris plants were grown hydroponically, and different concentrations of ABA in combination with catalase enzyme or ascorbate were added to the nutrient solution. Catalase treatment had no effect by itself (no ABA) and had little or only a small stimulatory effect at ABA concentrations of 1, 50, and 100 mu M, but it partially inhibited the ABA effect at 5 mu M. Ascorbate by itself doubled J(v) and root hydraulic conductance over the control value. In the presence of ABA, ascorbate partially or, at 100 mu M, completely inhibited that ABA stimulation of J(v). These results are discussed in relationship to the possibility that ABA signaling in the roots involves ROS.