| Hydroponic cultures were conducted to investigate the effect of excessive Cu on the growth and Cu accumulation of Sudan grass (Sorghum sudanense) and garland chrysanthemum (Chrysanthemum coronarium L.). Results showed that Cu treatment decreased significantly root elongation, dry biomass and leaf chlorophyll contents and increased significantly the root electroy leakage. Compared with Sudan grass, the dry biomass of garland chrysanthemum was considerably lighter than that of sudan grass at the same Cu concentration treatment. The shoots of garland chrysanthemum had significantly higher concentrations of total and water-soluble Cu than those of sudan grass. With 50μmol·L-1 Cu treatment, the Cu concentration was 64 mg·kg-1 in shoots of garland chrysanthemum, but that was only 24 mg·kg-1 in shoots of sudan grass. The roots of both species accumulated more Cu than the shoots in all Cu treatments. Most of the Cu in the roots was found on the cell walls. But, the concentration and proportion of Cu on the cell walls in Sudan grass were higher than that in garland chrysanthemum. The uronic acid in roots of sudan grass increased singinificantly with the increasing of Cu concentration in treatment solution and was highter than that of garland chrysanthemum with the same treatment. Cu treatment increased the concentrations of total non-protein thiols (NPT) in the shoots of garland chrysanthemum, but had no effects on that of sudan grass.The effects of the application of biodegradable (EDDS) and nondegradable chelate (EDTA) on the uptake of Cu, Zn, Pb and Cd by Sudan grass (Sorghum sudanense), corn (Zea mays L.), soybean (Glycine max L.), garland chrysanthemum (Chrysanthemum coronarium L.), and Chinese cabbage (Brassica chinesis L.) plants were studied using pot experiments. 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 enhancing uptake of Cu by the plants. But for Pb, the EDDS was less effective than EDTA. Among five plant species tested, the uptake of Cu by garland chrysanthemum was highest. The concentration and total uptake amount of Cu by shoots of garland chrysanthemum reached 973 mg·kg-1 and 909μg·pot-1 on day 5 after EDDS application, respectively. The concentrations of water-soluble Cu, Zn, Pb and Cd in soil decreased with time after the chelate application, the decreases were more pronounced in the soil treated with EDDS than with EDTA. 8 monthes after EDDS treatment, the effects of EDDS on shoot dry weight and heavy metal content in shoots were not significant. The results suggested that EDDS can be regarded as a good chelate candidate for the environmentally safe phytoextraction of heavy metals, particularly for Cu, in contaminated soils.Hydroponic cultures were conducted to investigate the effects of biodegradable chelating agent EDDS (S,S-ethylenediaminedisuccinic acid) on the growth and Cu uptake by garland chrysanthemum (Chrysanthemum coronarium L.), a sensitive plant species to soil chelant amendment. In the presence of 50μmol·L-1 of Cu, the addition of EDDS resulted in the increases of shoot and root biomass (DM), and the decrease of the relative electrolyte leakage rate of root cells and the concentration of Cu in shoots. When the roots were pretreated with 65℃water for 0.5-2h or with 0.001-0.1 mol·L-1 HCl for 24h before the exposure to 50μmol·L-1 of Cu + 100μmol·L-1 of EDDS, the concentration of Cu in shoots increased considerably compared with the shoots without any pretreatment. A statistically positive correlation was found between the Cu concentration in shoots with the relative electrolyte leakage rate of root cells. The result indicated that Cu-EDDS might be less bioavailable form to plants, and some physiological damages to the roots were much useful to enhance the accumulation of Cu in plant shoots.
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