Phytotoxic effect of aluminium on maize root membranes
1999
Pavlovkin, J. (Slovak Academy of Sciences, Ivanka pri Dunaji (Slovak Republic). Institute of Experimental Phytopathology and Entomology) | Mistrik, I.
In this study, the effect of Al on the electrical membrane potential (Em) of outer cortex root cells of three-day-old maize seedlings has been studied. The Em values of root cells ranged between - 115 and - 146 mV.Em of older cells towards the root base was considerably more negative than that of the young root tip cells. Experiments with NaCN + SHAM revealed that the diffusion potential (Ep) of root tip cells is smaller than that of root base cells. In short term experiments Em has been rapidly and significantly depolarized by Al. The depolarization was concentration dependent and reached the maximum at 150 micro M Al. The extent of membrane depolarization by 100 micro M Al decreased continuously from the apex to the base of the root. Simultaneously, the number of cells without any response to Al considerably increased in the region from 10 to 35 mm behind the root tip. Interestingly, this apparent intensivity correlated well with the differentiation of the known maize root exodermis. No Em changes have been observed in cells more distant than 40 mm from apex. The sensitivity of the cells to Al decreased in radial direction and when the tip of the microelectrode reached the interior of the central cylinder Al induced no Em changes. Both the P-ATPase activator fusicoccin (FC) and glucose diminished the depolarizing effect of Al on Em. Exposure of roots to Al treatment retarded K+ efflux from root tip segments and had no effect on K+ efflux from segments of root base. The present results suggest that, in short-term experiments, Al does not directly affect the electrogenic plasma membrane H+ATPase
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