Heavy metal availability in pelargonium hortorum rhizosphere: Interactions, uptake and plant accumulation

Abstract

The rhizosphere is a key area for the plant metal uptake. We studied heavy metal availability in the rhizosphere and the bulk soil, the interactions between metal ions, and their effects on heavy metal uptake and accumulation by Pelargonium hortorums (geranium). A pot experiment with plants of geranium was conducted in a soil spiked with cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) singly or in combinations. Bulk soils showed higher concentrations of extractable metals than rhizosphere soils, and metals accumulated preferentially in roots relative to aerial biomass. Regression analysis showed that soil extractable Cr, Ni and Pb were related (R2 = 0.90) to their concentration in plants, but there was no correlation between soil and plants for Cd, Cu, and Zn. Larger concentrations of metals were found when they were added in combinations rather than individually, and availability and uptake were directly related to the level of metals applied.