Absorption And Utilization Of Vetiveria Zizanioide On Insoluble Zn And Cd In Alkaline Soil And Regulatory Mechanism Of EDTA

Phytoremediation is a kind of environment management technique which uses plant to purify, blunt or fix environment contaminants to remove or reduce environment contamination. Pot experiments (rhizobag) were carried out to investigate the influence of Zn and Cd absorption,and utilization by vetiveria zizanioide , and the regulatory mechanism of EDTA in alkaline soil(calciferous purple soil). The effect of vetiveria zizanioides and root exudates on the insoluble Zn and Cd were also study in order to provide theory basis on soil Zn and Cd contamination phytoremediation.The plant growth of vetiveria zizanioides was inhibited by the insoluble Zn and Cd in different extent. The inhibitation on plant growth was in the order of Zn and Cd compound contamination(The dry weights of shoot and root decreased by 10.9% and 19.0% at 75d, 9.4% and 24.2% at 90d, respectivily) Cd＞Zn. It suggested that the inhibitation on plant growth increased with the increases of toxicity of heavy metals.The supplying EDTA accelerateed effects of heavy metals on vetiveria zizanioides growth(The dry weights of shoot and root declined by 4.6%～18.0% and 10.6%～24.2%, respectivily) .The activities of superoxide dismutase (SOD), peroxidase(POD) and catalase(CAT) of the shoot and root significantly increased with increasing of Zn and Cd toxicity. The root system vigor of vetiveria zizanioides and the contents of chlorophyll a and b decreased while the contents of proline, glutathione(GSH) and the malondialdenvde(MDA) of leaves increased. After supplying EDTA, the enzyme activities, proline, GSH of leaves, the contents of water-soluble Proteins and MDA all decreased, while the contents of chlorophyll a and b increased.The uptake of N derceased by the insoluble Zn and Cd, and the uptake of Pand K decreased by the insoluble Cd , while the uptake of P and K increased by the insoluble Zn. The uptake and transferation of P and K were inhibited by EDTA In this experiment, Zn and Cd showed different interaction when the concentration ratio of Zn and Cd in soil, The relationship between Zn and Cd showed restraint when the concentration ratio of Zn and Cd in soil is significant different, while the relationship between Zn and Cd showed synergistic action when the concentration ratio of Zn and Cd in soil is near. EDTA had significant regulation to the uptake of the two heavy metals.The highest contents of total N.available N, P and K in rhizosphere were found in the treatments of Zn and Cd interaction, the second was the Zn or Cd treatment. The tendency of available N, P and K contents in non-rhizosphere had similar to those in rhizosphere. The available N and P contents in rhizosphere increased, by supplying EDTA, but no significant effect on available K was observed. The available Zn contents in rhizosphere were in the order of Zn＞Zn+Cd＞Cd (at 75d) or Zn +Cd＞Zn＞Cd (at 90d), while Cd contents in rhizosphere were in the order of Zn+Cd＞Cd＞Zn. The available Zn contents in rhizosphere of Zn and Cd interact treatments and available Cd contents of Zn and Cd interact treatments and single Cd treatments increased with the growing period.After supplying EDTA, the available Zn and Cd contents in rhizosphere both increased significantly. PH of rhizosphere was lower than that of non-rhizosphere because of the emerging of the root exudates . The pH of rhizosphere declined with the growing period,and the pH of rhizosphere is in the order of CK＞Zn＞Cd＞Zn and Cd interactive treatment in the same growing period.The root exudates of Vetiveria zizanioides under the heavy metals stress had significant activation to the same heavy metals. As for activating insoluble Zn in soil, root exudates of Zn pollution , Zn and Cd compound pollution were higher than that of Cd pollution, while the activating insoluble Zn of root exudates of Cd pollution, Zn and Cd compound pollution were higher than that of Zn pollution The activation of EDTA on insoluble heavy metals was significant higher than that of the other treatments(In the three soils.the activation to Zn and Cd increased about 41.7,28.3 and 26.8 times, 10.3, 218.8 and 139.2 times,respectively).The activations of Vetiveria zizanioides root exudates under normal incubation conditions to the insoluble heavy metals Zn and Cd in soil were not significant.