Interactions between cadmium uptake and phytotoxic levels of zinc in hard red spring wheat

Wheat grown on cadmium (Cd)-uncontaminated soils can still potentially translocate unacceptable levels of Cd to grain. The effect of zinc (Zn) and Cd levels on Cd uptake and translocation in "Grandin" hard red spring wheat (HRS-wheat) (Triticum aestivum L.) was investigated using a double chelator-buffered nutrient solution [EGTA-used to buffer Cd, Zn, copper (Cu), manganese (Mn), and nickel (Ni); and Ferrozine (FZ) used to buffer Fe2+]. In the Zn level series of treatments, Cd2+ activity was held constant at 10(-10.7) M, and the Zn2+ activity was varied from 10(-7.6) to 10(-5.2) M. As Zn2+ activity increased, the translocation of Cd to the shoots decreased. The shoot: root Cd concentration ratio decreased from 0.20 to 0.03 as pZn(2+) went from 7.6 to 5.2, indicating that adequate to high levels of Zn are effective in reducing Cd translocation to the shoots of "Grandin" HRS-wheat. In the Cd series, the Zn activity was at 10(-6.6) M, while Cd activity was increased from 10(-10.7) to 10(-9.2) M. High levels of Cd did not significantly affect the uptake and translocation of Zn in the roots and shoots. While at pCd(2+) of 9.2, the root and shoot Cd concentrations significantly increased, there was not a significant increase in the shoot: root Cd ratio. This would indicate that even at high Cd2+ activities, Zn is effective in regulating Cd uptake and translocation in "Grandin" HRS-wheat.