Physiological Response To Lead Stress And Phytoremediation Of Lead Contaminated Soil By Chenopodium Ambrosioides L.

A series experiment were conducted to study the growth responses, the physiological reaction of Chenopodium ambrosioides L. to lead stress, and the influences of growing plants on lead distribution over the soil, the results were as follows:The seed germination rate was slightly increased at 50mg · L^-1 lead treatment, and then greatly decreased when exposure to higher lead concentrations, it was only 53 percent of control group under 450mg · L^-1 lead treatment. The elongation of radicle was greatly inhibited under lead stress, the radicle and hypocotyls were injured and even died at 100mg· L^-1 concentrations of lead. The hypocotyls could not elongate at 300mg· L^-1 lead concentrations, thus the cotyledon could not come out of seed coat, and the germinate process terminated.Greenhouse study, pot experiment was conducted to evaluate growth response and Pb phytoextraction of Chenopodium ambrosioides L. in contaminated soils. The results from this study indicate that the plant exhibited high tolerance to Pb toxicity in the soil; the normal growth and chlorophyll content were attained under 3850mg· kg^-1 total Pb treatment. The Pb concentrations in roots was much higher than that in shoots, the plant height was decreased along with the increase of lead concentrations. The lead accumulation capacity of single plant increased at the lead concentrations range from 560mg· kg^-1 to 3850mg· kg^-1 in soil, and then decreased when treated with higher concentration of lead.The available contents of Pb increased while the residual form of Pb decreased when Chenopodium ambrosioides L. were planted in the soil. 3.74 percentage of total Pb in 1048mg· kg^-1 Pb-applied soils and 1.73 percentage in 3850mg· kg^-1 Pb-applied soil were reduced respectively after phytoextraction and removal by Chenopodium ambrosioides L. for three months.The SOD, POD and CAT activity in leaves of Chenopodium ambrosioides L. all gradually increased along with the increase of lead concentrations, but decreased later at higher concentrations of lead. The SOD and POD activity exhibited an increase -decrease -increase trend with the extent of lead stress, but the CAT activity was not changed significantly during the course. The MDA contents in the leaves increased along with the increase of lead concentrations.The 2D-electrophoresis was used to analyze the differential protein expression pattern in the leaves of Chenopodium ambrosioides L. with and without lead treatment. The research showed most of the proteins expressed stably, however, seven protein spots were found only in the gel image of leaves with lead treatment. They were: A (14.9kD,pI5.71) ,B(14.4Kd, pI3.50), C(14.4kD,pI4.21), D(14.7kD,pI4.30), E(14.2KD,PI4.57), F(103.2kD,pI3.54)and G(25.8kD,pI4.59). They might act important roles in resistance to lead stress.