Lead-induced genotoxicity to Vicia faba L.roots in relation with metal cell uptake and initial speciation
Résumé
Formation of organometallic complexes in soil solution strongly influence metals phytoavailability. However, only few studies deal with the influence of metalspeciation both on plant uptake and genotoxicity. In the present study, Viciafaba seedlings were exposed for 6 h 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 leaduptake 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 (r2=0.65). In contrast, a strong relationship (r2=0.93) exists between Pb2+ 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 leadgenotoxicity or uptake. These results demonstrate that metalspeciation knowledge could improve the interpretation of V. fabagenotoxicity test performed to test soil quality.
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