Responses And Potential Remediation Of Two Species Of Ground Cover Plants To Cd And Pb Stress

This paper is about the effects of single and compound treatments of Cd and Pb on Polygonatum odoratum and Pilea cadierei Gagnep. et Guill, focusing on their growth, physiological responses and heavy metal accumulation to different concentrations of Cd and Pb. This study provided the theoretical background for both heavy metal toxicity mechanisms and phytoremediation to heavy metal ground. The main results are as follows:(1) The biomass of Polygonatum odoratum at first increased and then decreased under single treatments of Cd. The root of Polygonatum odoratum increased at low Cd concentrations and decreased at high Cd concentrations; moreover, it was inhibited by single treatments of Pb and compound treatments of Cd and Pb. Under the single treatments of Cd and Pb, The biomass of Pilea cadiereit frist increased and then decreased. Under the concentration increasing of compound treatments of Cd and Pb, its biomass decreased gradually. With the concentrations increasing of single Cd and Pb, The root tolerance index of Pilea cadiereit increased at first and then decreased. Under compound treatments, the root decreased gradually.(2) It was a slow process for heavy metal to injury the plant, high concentrations and long time stress could cause the decrease of chlorophyll contents of the two kinds of plant. Under single and compound treatments of Cd and Pb, the net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Cond) and intercellular CO2 concentration(Ci) of Polygonatum odoratum increased at low concentrations and decreased at high concentrations. With the concentration increasing of single Cd and Pb, Pn and Tr of Pilea cadiereit increased at first and then decreased, but gradually decreased under compound treatments.(3) With the concentration increasing of single and compound treatments Cd and Pb, the activities of SOD, POD and the content of proline, MDA increased in different degree. High concentration and long time stress of heavy metal resulted the decrease of activities of SOD and content of proline in Polygonatum odoratum as well as the activities of SOD, POD in Pilea cadiereit.(4) For Polygonatum odoratum and Pilea cadierei, the content of Cd and Pb in root, stem and leaves increased with increasing of single and compound concentrations and was mainly accumulated in root. Under compound treatments, the accumulation of Pb in aboveground of two kinds of plant had a greatly improve to single treatments of Cd and Pb.Compositively, as the main pollutant in heavy metal gound, Cd and Pb had an obviously effect on Polygonatum odoratum and Pilea cadierei. Compared with the variation of all the characteristics, both of them could affect phytoremediation to complicated heavy metal ground. Polygonatum odoratum which had a high tolerance to Pb should be considered as a kind of valuable plant and used in Pb polluted gound.