Computation of surface electrical potentials of plant cell membranes. Correspondence to published zeta potentials from diverse plant sources

摘要

A Gouy-Chapman-Stern model was developed for the computation of surface electrical potential (psio) of plant cell membranes in response to ionic solutes. The present model is a modification of an earlier version developed to compute the sorption ofions by wheat (Triticum aestivum cv. Scout 66) root plasma membranes. A single set of model parameters generates values for psio that correlate highly with published zeta potentials of protoplasts and plasma membrane vesicles from diverse plant sources.The model assumes ion binding to a negatively charged site (R- = 0.3074μmol m-2) and to a neutral site (PO = 2.4μmol m-2) according to the reactions R- + IZ % RIZ-1 and PO + IZ % PIZ, where IZ represents an ion of charge Z. Binding constants for the negative site are 21 500 M-1 for H+, 20 000 M-1 for Al3+, 2200 M-1 for La3+, 30 M-1 for Ca2+ and Mg2+, and 1 M-1 for Na+ and K+. Binding constants for the neutral site are 1/180 the value for binding to the negative site. Ion activities at the membrane surface, computed on the basis of psio, appear to determine many aspects of plant-mineral interactions, including mineral nutrition and the induction and alleviation of mineral toxicities, according to previous and ongoing studies.