The Mechanisms Of Cu Tolerance And The Potential In The Phytoremediation Of Elsholtzia Haichowensis

Hydroponic cultures were conducted to investigate the absorption and accumulation of copper and the copper tolerance mechanisms of Elsholtzia haichowensis, after different copper concentration treatments. A pot study was conducted to investigate the potential of Elsholtzia haichowensis for phytotemediation of contamianated soils.The results showed that Cu at 100 and 200μM significantly decreased the root dry weight of E. haichowensis,, but had no signifciant effect on shoot dry weight. Root growth was more effectively restrained by copper than shoot growth. The plants grown in the presence of 200 uM Cu accumulated 288 and 7626μg g^-1 DM in the shoots and roots, respectively. A greater proportion of accumulated Cu was water-soluble, accounting for 42-93 % and 15-24 % of the total Cu in the shoots and roots, respectively.The concentrations of reduced glutathione (GSH) and protein thiols and the free amino acid significantly increased under excess Cu supply. However, the concentrations of these compounds, particularly protein thiols, were much higher in the leaves than in the roots. Three UV-absorbing peaks could be eluted out through gel filtration chromatography on Sephadex G-50. A large amount of Cu was detected in the UV-absorbing peaks in 40-50 and 70-90 ml elution fractions of the root extract and in 40-50 and 120-140 ml elution fractions of the leaf extract. The results suggested that the adaptive Cu tolerance mechanism in E. haichowensis might involve the active participation of protein thiols, which have more important roles in the leaves than in the roots.With the increasing copper concentration in the solution, the malondialdehyde (MDA) concentration increased in the roots of Elsholtzia haichowensis, whereas had no significant effect in the leaves. The activities of SOD,POD,CAT,APX,GR increased with the increasing copper concentration in the roots of Elsholtzia haichowensis, while in the leaves the activities of SOD,POD only increased. Except CAT, the activities of these antioxidative enzymes were much higher in the roots than in the leaves. The results showed that system of antioxidative enzymes was important to defense oxidative strees.The results showed that the application of 5 mmol·kg^-1 EDDS and EDTA to the soil significantly increased the concentrations and total uptake amounts of Cu, Zn, Pb and Cd in the shoots of all plant species. EDDS was more effective than EDTA at solubilizing soil Cu and Zn and enhancing uptake of Cu and Zn by the plants. But for Pb and Cd, the EDDS was less effective than EDTA.