| Phytoremediation refers to the hyperaccumulator uptakes and accumulates thesuperabundant heavy metal of the contaminated soil and then by harvesting plants, reducesthe content of heavy metals in the soil so as to achieved ecological restoration, which is themost scientific and effective methods in the remediation of heavy metal contaminated soil.The chelating agent can effectively activate heavy metals in the soil, and contributes to theenrichment of heavy metals by plants, so it is widely used to strengthen the repairement of theplant extract of heavy metals from soil. In this study, through pot experiment, Enrichmentcharacteristics on heavy metal cadmium (Cd), The physiological response to different levelsof heavy metal stress(0,10,20,30,40,50mg/kg soil）and effect of chelating heavy metal onthe absorption and transhipment regulation in white clover (Trifolium repens Linn.) wasconducted as to provide a scientific basis for white clover to be used in the restoration andgreenfield building on heavy metal contaminated soil. The main conclusions are as follows:(1)The effect of different cadmium concentrations on the cadmium absorptiontransportation capacity in white cloverUsing an atomic spectrophotometer, the heavy metal content of shoots and roots samplesfrom white clover were measured, It was discovered that with the increase in theconcentration of Cd, the cadmium content of white clover was trend to be stabilized after thefirst sharp rise in overall pattern, the cadmium content in the aboverground part was greaterthan that in the underground part and there were significant differences amang differentcadmium concentrations. Compared to the control, the cadmium content of aboveground andunderground portion in treatmentⅠ increased dramatically and in the aerial parts the increasereached to321.4%. After the Cd concentration reached to20mg/kg the cadmium content inunderground part had slowed down and basically maintained at a lever which was around theaboveground. It was clear that when, cadmium absorption ability of white clover was strangunder20mg/kg cadmium stress. The average transporter coefficient in different cadmiumstress was1.6814, and transport coefficients in the treatment groups were over1.6exceptcontrol, which indicated that white clover had the characteristics of cadmium enrichmentplants. (2)The effect of different concentrations of cadmium on the physiological characteristicsof white cloveWith the increasing of concentration of heavy metals cadmium, the content ofchlorophyll a and chlorophyll b and the total amount basically presented a trend of firstslightly rising and then levelling off. The content of MDA concentration showed an overallupward trend with cadmium stress increased and when cadmium concentrations in thetreatment V reached the highest was88.2%higher than the control, which indicated a moreserious injury. With the cadmium stress concentration rises the content of SOD, POD andCAT showed an overall upward trend and when the concentration reached to its maximum50mg/kg, the activity of SOD, POD and CAT group were higher than the control by156.4%,313.0%and149.2%so that the Cd toxic shamrocks was alleviated effectively.(3)The effect of chelating agents on the absorption of cadmium in white cloverDifferent concentrations of EGTA and EDDS were significantly improved the Cdabsorption of white clove.The Cd absorption in NTA treatment was significantly lower thanEGTA and EDDS. Different chelaters had a significant impact on the Cd absorption of whiteclove in the underground parts.Compared with the NTA, EGTA and EDDS significantlyimproved the Cd absorption of underground part in white clove. When chelater was at12mmol/kg, the absorption of cadmium in the white clove was reduced in all treatments. |
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