Bioelectrochemical studies of ionic influence on transport characteristics of primary root of Zea mays

Abstract

The bioelectric potential (BEP r ) was measured on root segments of Zea mays which acted as a membrane separating two electrolyte solutions ( m 1 , m 2 ). The BEP r was measured in the absence ( m 1 = m 2 ) and presence ( m 1 ≠ m 2 ) of a concentration gradient for chloride salts (NH 4 Cl, LiCl, NaCl, KCl) and HCl. The relationship BEP r = f (−log m 2 ) was non-linear, thereby excluding the diffusion potential as the main cause of biopotential generation. Roots treated with DNP showed a dramatic decrease of potential and a shift of zero potential value to lower concentrations. A parallel flame photometry analysis performed on intact roots revealed changes of internal Li + and K + concentrations in normal roots (low-salt) and K + concentrations in roots treated with DNP or killed with a cytological fixative. It was shown that the isotonic point for K + in normal roots coincides with the BEP r =0 point in the case of KCl. The difference between these two points in case of LiCl was assigned to internal K + contribution to the electrical isopotential. The comparison of biopotential and concentration data points to an active component of ionic transport in roots of Zea mays .