THE REGULATION OF ZINC UPTAKE IN WHEAT PLANTS

The control of net zinc-uptake rate can be a critical factor for plant survival and growth in heavy metal polluted environments. Here we rep ort the results of an study on the regulation of net Zn-uptake in whea t plants (Triticum aestivum L.) grown in solution culture at supra opt imum levels of Zn supply. As external Zn-concentration was increased, net Zn-uptake rate increased. The higher the external Zn-concentration the: higher both Zn-influx and efflux, with Zn-efflux increasing more . However the relative increase in the outward flux of Zn was not enou gh to prevent the potential increase of Zn-concentration within plant tissues up to toxic levels. On the other hand, when the external Zn-co ncentration was changed to a higher or a lower level, the unidirection al Zn-influx changed almost instantaneously, while the net uptake rate of Zn changed slowly, towards the level exhibited by plants kept in t he previous solution. These findings are consistent with the concept t hat regulation of Zn fluxes. at supra optimum levels of Zn supply, app ear to be controlled primarily by Zn-efflux and not by short or long t erm regulation of Zn-influx. (C) 1998 Published by Elsevier Science Ir eland Ltd. All rights reserved.