Abstract
The effects of zinc and cadmium on the growth, mineral composition (P, K, Ca, Mg, Fe, Zn, Mn, and Cu), and metal accumulation by lupine (bluebonnet, Lupinus uncinatus Schldl.) were investigated in a hydroponics experiment. Plants were exposed to increasing concentrations of Zn (0, 30, 40, and 50 mu M) and Cd (0, 3, 4, and 5 mu M) for 1 week. The species showed different patterns of metal accumulation and distribution in the plant parts, suggesting different mechanisms of metal tolerance for each metal. At the highest doses of Zn and Cd, the amounts of metals accumulated in roots, stems, and leaves were 1,289, 1,918, and 1,132 mg kg(-1) dry matter and 2,467, 227, and 164 mg kg(-1) dry matter, respectively. The shoot:root Zn ratios obtained for 50, 40, and 30 mu M treatments were 2.36:1, 2.28:1, and 2.32:1, respectively, whereas the ratio in case of Cd remained < 1 for the three Cd treatments. No significant effect on plant dry biomass was observed in either of the cases. Significant changes in plant mineral composition occurred, however, concentrations were generally above the deficiency levels. This suggests that this species may tolerate Cd without its hyperaccumulation and shows exclusion mechanism of Cd tolerance.