Lead-induced genotoxicity to Vicia faba L. roots in relation with metal cell uptake and initial speciation.

Formation of organometallic complexes in soil solution strongly influence metals phytoavailability. However, only few studies deal with the influence of metal speciation both on plant uptake and genotoxicity. In the present study, Vicia faba seedlings were exposed for 6h in controlled hydroponic conditions to 5 µM of lead nitrate alone and chelated to varying degrees by different organic ligands. Ethylenediaminetetraacetic acid and citric acid were, respectively, chosen as models of humic substances and low weight organic acids present in natural soil solutions. Visual Minteq software was used to estimate free lead cations concentration and ultimately to design the experimental layout. For all experimental conditions, both micronucleus test and measure of lead uptake by plants were finally performed. Chelation of Pb by EDTA, a strong chelator, dose-dependently increased the uptake in V. faba roots while its genotoxicity was significantly reduced, suggesting a protective role of EDTA. A weak correlation was observed between total lead concentration absorbed by roots and genotoxicity (r(2)=0.65). In contrast, a strong relationship (r(2)=0.93) exists between Pb(2+) concentration in exposure media and genotoxicity in the experiment performed with EDTA. Citric acid induced labile organometallic complexes did not demonstrate any significant changes in lead genotoxicity or uptake. These results demonstrate that metal speciation knowledge could improve the interpretation of V. faba genotoxicity test performed to test soil quality.

Assessment of the genotoxicity of Cu and Zn in raw and anaerobically digested slurry with the Vicia faba micronucleus test.

Genotoxicity of Cu and Zn was assessed by use of the micronucleus (MN) test on Vicia faba roots. Plants were exposed to various leachates of raw and anaerobically digested pig slurry, with maximum total concentrations of 200microM Cu and 600microM Zn. The results indicated stabilisation of the organic matter during anaerobic digestion of the slurry and bioconversion of some phytotoxic organic compounds (e.g. phenols or p-cresol), but did not show a relationship between Cu and Zn concentrations and MN frequency. Exposure of Vicia plants to binary inorganic solutions of Cu and Zn (CuSO(4)/ZnSO(4), 1:3) showed a significant micronucleus induction at concentrations of 40microM Cu and 120microM Zn and higher. When MN frequency was plotted against dissolved Cu (<0.45microm), applied as slurry or as CuSO(4), a single curve was obtained. At concentrations lower than 10microM, modulation of the genotoxic effect of Cu was found. At concentrations up to 150microM, MN induction increased significantly, while phytotoxic symptoms appeared at higher concentrations.