Computation of surface electrical potentials of plant cell membranes: correspondence to published zeta potentials from diverse plant sources
1998
Kinraide, T.B. | Yermiyahu, U. | Rytwo, G.
A Gouy-Chapman-Stern model has been developed for the computation of surface electrical potential of plant cell membranes in response to ionic solutes. The present model is a modification of an earlier version developed to compute the sorption of ions by wheat (Triticum aestivum L. cv Scout 66) root plasma membranes. A single set of model parameters generates values for surface electrical potential 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- = 0.3074 micromoles m-2) and to a neutral site (p0 = 2.4 micromoles m-2) according to the reactions R- + I(Z) reversibly RI(Z-1) and p0 + I(Z) reversibly PI(Z), where I(Z) 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+, 2,200 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 surface electric potential, 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. A computer program with instructions for the computation of surface electrical potential, ion binding, ion concentrations, and ion activities at membrane surfaces may be requested from the authors.
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