In vivo treatment of barley roots with vanadate increases vacuolar H⁺-translocating ATPase activity of the tonoplast-enriched membrane vesicles and the level of endogenous ABA

Evidence for an increase in the activity of the vacuolar H⁺-translocating ATPase of barley roots, accompanied by qualitative change, in response to exogenously applied abscisic acid (ABA) has been reported previously [Kasai et al. (1993b) Plant Cell Physiol. 34: 1107]. In the present study, such an increase in the H⁺-translocating ATPase activity was shown to occur upon treatment of barley roots with vanadate. Furthermore, the level of endogenous ABA in the roots was shown to increase significantly as a result of this treatment. The present observations provide further support for the proposed physiological significance of cellular ABA in the regulation of the vacuolar H⁺-translocating ATPase activity.