Abstract
It is assumed that toxic effect of the medium is well correlated with the concentration of rhizotoxic ions at the plasma membrane (PM) surface than that in the bulk phase because target molecules of the rhizotoxic ions are localized in the PM surface. Using Gouy-Chapman Stern model and the ion speciation, we estimated Al activity at the PM surface and bulk-phase solutions with different pH. Bulk-phase Al in the solution at pH 5.5 was much lower than pH 5.0, but it maintained Al activity at the PM surface. Both media totally inhibited growth of Al hyper-sensitive KO mutants. Furthermore, one of the most sensitive gene in terms of the response to Al, AtALMT1 encoding the Al inducible malate transporter, was induced in the WT root. It suggests that Al at the PM surface is important index to evaluate rhizotoxicity of Al.
