Computation of Surface Electrical Potentials of Plant Cell Membranes
Correspondence to Published Zeta Potentials from Diverse Plant Sources

Thomas B. Kinraide^*, Uri Yermiyahu, and Giora Rytwo

Appalachian Soil and Water Conservation Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Beaver, West Virginia 25813-0400 (T.B.K.); Institute of Soils, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet-Dagan 50250, Israel (U.Y.); and Tel Hai College, Upper Galilee 12210, Israel (G.R.)

A Gouy-Chapman-Stern model has been developed for the computation of surface electrical potential (₀) 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 ₀ that correlate highly with published  potentials of protoplasts and plasma membrane vesicles from diverse plant sources. The model assumes ion binding to a negatively charged site (R = 0.3074 µmol m²) and to a neutral site (P⁰ = 2.4 µmol m²) according to the reactions R + I^Z  RI^{Z1 and} P⁰ + I^Z  PI^Z, where I^Z represents an ion of charge Z. Binding constants for the negative site are 21,500 M¹ for H⁺, 20,000 M¹ for Al³⁺, 2,200 M¹ for La³⁺, 30 M¹ for Ca²⁺ and Mg²⁺, and 1 M¹ 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 ₀, 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 ₀, ion binding, ion concentrations, and ion activities at membrane surfaces may be requested from the authors.

Plant Physiol. (1998) 118: 505-512
Copyright Clearance Center:   0032-0889/98/118//08
© 1998 American Society of Plant Physiologists

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