PT - JOURNAL ARTICLE AU - Kinraide, Thomas B. AU - Ryan, Peter R. AU - Kochian, Leon V. TI - Interactive Effects of Al<sup>3+</sup>, H<sup>+</sup>, and Other Cations on Root Elongation Considered in Terms of Cell-Surface Electrical Potential AID - 10.1104/pp.99.4.1461 DP - 1992 Aug 01 TA - Plant Physiology PG - 1461--1468 VI - 99 IP - 4 4099 - http://www.plantphysiol.org/content/99/4/1461.short 4100 - http://www.plantphysiol.org/content/99/4/1461.full SO - Plant Physiol.1992 Aug 01; 99 AB - The rhizotoxicities of Al3+ and of La3+ to wheat (Triticum aestivum L.) were similarly ameliorated by cations in the following order of effectiveness: H+ ≈ C3+ &gt; C2+ &gt; C1+. Among tested cations of a given charge, ameliorative effectiveness was similar except that Ca2+ was slightly more effective than other divalent cations and H+ was much more effective than other monovalent cations. H+ rhizotoxicity was also ameliorated by cations in the order C3+ &gt; C2+ &gt; C1+. These results suggest a role for cell-surface electrical potential in the rhizotoxicity of Al3+, La3+, H+, and other toxic cations: negatively charged cell surfaces of the root accumulate the toxic cations, and amelioration is effected by treatments that reduce the negativity of the cell-surface electrical potential by charge screening or cation binding. Membrane-surface activities of free Al3+ or La3+ computed according to a Gouy-Chapman-Stern model correlated well with growth inhibition, which correlated only poorly with Al3+ or La3+ activities in the external medium. The similar responses of Al-intoxicated and La-intoxicated roots to ameliorative treatments provide evidence that Al3+, rather than AlOH2+ or Al(OH)2+, is the principal toxic species of mononuclear Al. Comparisons of the responses of Al-sensitive and Al-tolerant wheats to Al3+ and to La3+ did not support the hypothesis that varietal sensitivity to Al3+ is based upon differences in cell-surface electrical potential.