EFFECTS OF CADMIUM AND LEAD ON THE ACCUMULATION OF CA-2+ AND K+ AND ON THE INFLUX AND TRANSLOCATION OF K+ IN WHEAT OF LOW AND HIGH K+ STATUS

The effects of cadmium and lead on the internal concentrations of Ca2+ and K+, as well as on the uptake and translocation of K1(Rb-86+) were studied in winter wheat (Triticum aestivum L. cv. MV-8) grown hydroponically at 2 levels of K+ (100-mu-M and 10 mM). Cd2+ and Pb2+ were applied in the nutrient solution in the range of 0.3 to 1000-mu-M. Growth was more severely inhibited by Cd2 1 and in the high-K+ plants as compared to Pb2+ and low-K+ plants. Ions of both heavy metals accumulated in the roots and shoots, but the K1 status influenced their levels. Ca2+ accumulation was increased by low concentrations of Cd2+ mainly in low-K+ shoots, whereas it was less influenced by Pb2+. The distribution of Cd2+ and Ca2+ in the plant and in the growth media indicated high selectivity for Cd2+ in the root uptake, while Ca2+ was preferred in the radial and/or xylem transport. Cd2+ strongly inhibited net K1 accumulation in high-K1 plants but caused stimulation at low K+ supply. In contrast, the metabolism-dependent influx of K1(Rb-86+) was inhibited in low-K+ plants, while the passive influx in high-K+ plants was stimulated. Translocation of K+ from the roots to the shoots was inhibited by Cd2+ but less influenced in Pb2+-treated plants. It is concluded that the effects of heavy metals depend upon the K+-status of the plants.