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 μM) and Cd (0, 3, 4, and
5 μM) 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 μM
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.