| In order to select the Cd-accumulated plants which had high tolerance and accumulation of Cd, the plants with high Cd content, big biomass and high pollution levels growed naturally in Kuimei tungsten mine in Gannan were taken as tested plants to analyze. The seclected Cd-accumulated plants were studied respectively in pot experiments and hydroponic experiments under adding various kinds of chelating agent and nutrients to obtain the phytoremediation of Cd-contaminated soils and provide basis material and scientific bases for control Cd-contaminated soils. The following results were observed:1. The results showed that 37 species of plants had been found in Kuimei tungsten mine belonging to 21 families and 37 genuses, mostly were the herbaceous plants and mainly the Composite and Grass family. Hyperaccumulator of Cd were not found in these plants, but the contents of Cd in 15 species of plants were more than 10 mg/kg, that in the aerial organs of the Ageratum conyzoides L was the highest which up to 67.70 mg/kg(the concentration factor and transfer coefficient respectively were 2.35 and 2.66, approaching the standard of hyperaccumulator. The Cd contents in the aerial organs of Conyza Canadensis L, Corchoropsis tomentosa (Thunb.) Mak, Gynura crepidioides Benth, Ageratum conyzoides L, Bidens pilosa Linn and so on were all more than that in the underground part, both the concentration factor and transfer coefficient were more than 1. These plants could be used as potential plants to control Cd-contaminated soils.2. Under low Cd concentration (<5 mg·L-1), the germination of the Gynura crepidioides Benth seeds had been promoted while in high Cd concentration, the germinativeforce, germination rate, germination index and vigor index were markedly reduced, showed extremely significant difference(P<0.01). Seed germination had been restrained under high concentrations of Cd, resulting in toxicological effects.3. For Gynura crepidioides Benth to water culture experiments, with the increase of Cd concentration, Gynura crepidioides Benth plant height, root length, biomass and patience of the index deal with the increasing concentration of Cd decreased gradually, but at low Cd concentrations (<5 mg·L-1) treatment under the growth of wild Chrysanthemum little effect. Adding nutrient elements and chelating agents on the growth of beneficial plant biomass. Gynura crepidioides Benth is much higher than the Mass Transit Department of shoot Cd concentration,indicating a stronger effect of root absorption. Three sets of tests of chlorophyll a, chlorophyll b, carotenoids and chlorophyll a+b reached at maximum under Cd treatment 25mg·L-1.4. The long-term pot experiment were carried out to study the Bidens pilosa Linn tolerance of plant growth and physiological characteristics.The results showed that the control group, added nutrient test and the chelating agent EDTA at a low Cd contamination conditions (<10 mg·kg-1) plant biomass highest, adding nutrients NPK is better than chelating agent EDTA, the higher the concentration is to dampen demand. Three sets of experiments, Bidens pilosa L. plant shoot Cd concentration> 100 mg·kg-1 under 10 mg·kg-1, and the enrichment coefficient is greater than 1, indicating Bidens pilosa L. is a relatively Good Cd hyperaccumulator.5. The long-term pot experiment were carried out to study the Ageratum conyzoides L.tolerance of plant growth.The results showed that the control group, and added nutrient test have more conducive to the growth of plant biomass under 10 mg·kg-1, and plant shoot Cd content close to 100 mg·kg-1 under 10 mg·kg-1, as the higher the concentration of added Cd, plants to absorb the higher Cd concentration, and the enrichment factor were more than 1, indicating Ageratum conyzoides L. is a good Cd enrichment plant, but Bidens pilosa Linn have large biomass than Ageratum conyzoides L.from growth appeared and training to the end of the experiment with dry fade phenomenon, so as to be further studied hyperaccumulators.
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