Lead accumulation and it's effects on peroxidase activity, phenolic and flavonoid compounds in seedlings of Medicago sativa L.

Heavy metal pollution is one of the most important ecological problems in the whole world. According to the environmental protection agency (EPA)، Pb is the most common heavy metal contaminant in the environment. In this study the effects of Pb stress (0، 120، 240، 500، 1000 μM Pb) on 7 days seedlings of Medicago sativa L. were investigated in hydroponic culture. The our results indicated Pb accumulation in roots and aerial parts and an increasing trend in total biomass was observed with increas of Pb concentration in medium which reduced later. Compared with control seedlings، increase in the contents of MDA and H2O2 were observed in those the seedlings under Pb stress. Moreover، increase in total flavonoids content، and peroxidase activity in roots and shoots of the treated seedlings were observed under Pb stress. Content of total phenolics decreased in roots and increased in shoots comparing to than the control.