The Effect Of Pb And Zn Compound Stress On The Physiology And Heavy Metals Accumulation Of Two Kinds Of Medicago Plants

The effect of different concentration combination of Pb and Zn on the seed germination,the tolerance and Pb and Zn contaminated soil remediation potential of Medicago sativa and M.falcata were studied by pot culture.The main results were as follows:(1)The results of effect of different concentration combination of Pb and Zn on the seed germination of Medicago sativa and M.falcata showed that the germination potential and germination rate of M.sativa and M.falcata were lower than control.The seed germination index and vigor index of two species were inhibited by the high concentration and the combination treatment.Pb promoted the leaf length,root length and root number of M.sativa increased and inhibited the leaf length and root number of M.falcata.(2)The results of effect of different concentration combination of Pb and Zn on the physiological response of M.sativa and M.falcata showed that the Pb and Zn enhanced the concentrations of photosynthetic pigments in M.falcata.5mmol/kg Pb treatment promoted the photosynthetic pigment synthesis of M.sativa and chlorophyll a and chlorophyll b and carotenoids increased 17.8%,11.6%and 10.6%,respectively,compared with the control.The plants by increasing the activity of antioxidant enzymes to alleviated the toxicity of Pb and Zn.(3)The results of effect of different concentration combination of Pb and Zn on the anatomical structure of M.sativa and M.falcata showed that the anatomical ctructure of M.sativa and M.falcata have a negative impact by single Pb or Zn or their combination treatment and leaves and roots anatomical structure were damaded.While,the stress of Pb and Zn combination alleviate the toxicity of sigle Pb and Zn stress.Zn could alleviate the poisoning of Pb to the seedings to a certain extent,and vice versa.(4)The results of the effect of different concentration combination of Pb and Zn on the growth and accumulation of heavy metals of M.sativa and M.falcata showed that the tolerance index of M.falcata under the treatments of 7.5 mmol/kg Pb and 2.5mmol/kg Pb+7.5mmol/kg Zn increased and were 53%or 6%.The highest concentrations of Pb and Zn of M.sativa were 139.4?g/g and 1246.3?g/g DW,respectively.The highest concentrations of Pb and Zn of M.falcata were 203.5?g/g and 1401.7?g/g DW,respectively.The enrichment ability of Pb,Zn and Cd in M.sativa was better than M.falcata.In the whole,Pb and Zn accumulations of M.sativa and M.falcata increased as Pb and Zn levels enhanced,but not obvious enrichment of Cu.The results indicated that M.sativa and M.falcate were better Pb and Zn accumulation and tolerant species and could be used as phytoremediation of Pb/Zn mine area and Pb and Zn contaminated environment.