EFFECT OF ZN2+ ON WATER AND K+ FLUXES IN DETOPPED MAIZE PLANTS

Water and K+ fluxes were examined in detopped plants of Zea mays L. (c v. White Horse Tooth), which were grown and exuded on half-strength Lo ng Ashton nutrient solution containing the appropriate concentration o f Zn2+ at 20-degrees-C. In light-grown plants, 100 and 500 muM Zn2+ in creased both water and K+ fluxes in detopped maize plants whereas 1 00 0 muM Zn2+ inhibited both fluxes. In the dark-pretreated plants, 1 000 muM Zn2+ in the medium stimulated K+ flux. The fluxes of K+, Zn2+, Ca 2+ and Mg2+ were usually higher in detopped plants than in intact ones . At 1 000 muM Zn2+ in the exudation medium, Zn2+ concentration was hi gher in the xylem exudate of dark-pretreated plants than in roots of p lants maintained in light. The results are discussed in relation to th e influence of Zn2+ on the membrane permeability and transport in plan ts.