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