Author
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Kinraide, Thomas |
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Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/12/2002 Publication Date: 1/1/2003 Citation: KINRAIDE, T.B. THE CONTROLLING INFLUENCE OF CELL-SURFACE ELECTRICAL POTENTIAL ON THE UPTAKE AND TOXICITY OF SELENATE. PHYSIOLOGIA PLANTARUM. 2003. V. 177. P. 64-71. Interpretive Summary: Food plants are sometimes bred, selected, or managed with the intention of enhancing the uptake of desired nutrients (such as calcium or phosphorus) and reducing the uptake of dangerous toxicants (such as heavy metals). In contrast, high accumulation of toxicants is desired in plants used in phytoremediation (the cleansing of soils or waters with plants). Because the surfaces of plant cells are electrically charged, charged solutes (ions) are attracted or repelled. Different conditions in the rooting medium, either in nature or in experiments, cause the electrical charge of cell surfaces to change. The problem that is addressed in this study is that our understanding of the electrical basis of plant-ion interactions is based almost entirely upon experimental work with positively charged ions. Negatively charged ions have been neglected. This study demonstrates that a negatively charged ion, selenate (both a natural nutrient and toxicant), accumulates and expresses its toxicity in accordance with electrical theory and quantitative models for the theory. We now have a generally useful electrical theory for plant-ion interactions that will help predict plant responses to management practices and guide the selection, breeding, and engineering of plants for food and phytoremediation. Technical Abstract: Root elongation in wheat seedlings (Triticum aestivum L. cv. Atlas 66) was inhibited by micromolar activities of SeO42-. SeO42- inhibition was enhanced by supplementation of the rooting medium with CaCl2, MgCl2, SrCl2, or the reduction of pH. These solute treatments, as well as the addition of tris(ethylenediamine)cobalt3+, enhanced the uptake of Se by the roots. The results are interpreted to reflect an elevated PM-surface activity of SeO42- caused by solute-induced reductions of plasma-membrane (PM) surface negativity. (PM-surface electrical potential is sometimes measured electrophoretically as the zeta potential.) This study complements a much more extensive literature documenting the usefulness of an electrostatic model (Gouy-Chapman-Stern), but the usefulness is based almost entirely upon experiments with cations rather than anions. The close correspondence among uptake, intoxication, and model-computed SeO42- activity at the PM surface adds credibility to the model and the available parameters. |
