Differential Effects Of Zn Concentrations On Cr(Vi) Uptake By Twosalviniaspecies: Involvement Of Thiol Compounds

Floating ferns of the genusSalviniahave great potential for phytoremediation of heavy metals. To date, the effect of essential metals on the accumulation and transport of toxic metals by aquatic ferns has not been suitably established. The aim of this study was to compare the ability of floating leaves ofSalvinia minimaandSalvinia rotundifoliaspecies to accumulate Cr from Cr(VI solutions containing very low (0.02 mg L-1) and low (5 mg L-1) Zn concentrations. After 7-day metal-exposure period, results showed that Zn increased Cr accumulation inS. minimaleaves whereas inS. rotundifoliadecreased significantly. Contrarily Zn accumulation did not show great differences between species. This fact may indicate that Zn interfere Cr(VI) uptake byS. rotundifolia. Bioconcentration factor (BCF) and translocation factor (TF) were affected differently by Zn in bothSalviniaspecies. Membrane stability index (MSI) of bothSalviniaspecies was decreased significantly by 5 mg L-1Zn concentration. Zn ions also increased hydrogen peroxide accumulation in fronds ofSalviniaspecies. Total thiols (TT), non-protein thiols (NPT) and protein-bound thiols (PBT) were differentially affected by Cr(VI) and Zn ions. This study provides evidences on the involvement of different mechanisms against Cr(VI)/Zn toxicity inS. minimaandS rotundifoliaspecies.