Aluminum Stress Increases K+ Efflux and Activities of ATP- and PPi- Dependent H+ Pumps of Tonoplast-Enriched Membrane Vesicles from Barley Roots

Aluminum stress significantly stimulated K⁺ effux from barleyroots that had been preloaded with K⁺ The stress also increasedPP₁- and ATP-dependent H⁺ pump activities of tonoplast enrichedmembrane vesicles from the roots. Ca²⁺ ions reduced increasesin K⁺ effux and both H⁺ pump activities under these conditions. (Received April 25, 1992; Accepted August 4, 1992)