Abstract :
Lead (Pb) exists in many forms in natural source. According to the environmental protection agency (EPA), Pb is the most common heavy metal contaminant in the environment. In this study, response of 10 dill (Anethum graveolens) ecotypes to lead stress (0, 300 and 600 ?M Pb) was studied in hydroponic culture system. Plant growth parameters (RGR, AGR, NAR, LAD and RLGR), electrolyte leakage and proline were measured 30 days after stress induced by lead. Among the ecotypes, Ardabil, Shahreza and Esfehan showed significantly smaller reduction in growth parameters compared with the rest of the ecotypes, indicating that the former ecotypes were more lead tolerant than the others. Electrolyte leakage was increased under lead stress and the highest value was observed in Shahreza ecotype Electrolyte leakage showed contrary relation with growth parameters. Relative Water Content did not differ significantly under lead stress. Proline accumulation increased significantly in the leaves of all ecotypes under stress conditions. The highest proline accumulation was found in Esfahan ecotype under lead stress. Our observations demonstrate that proline accumulation is probably one aspect of heavy metal tolerance in plants.
