Pb-tolerance Mechanism Of Hypertolerant Plants Pogonatherum Crinitum And Isachne Globosa

With the development of industry and agriculture, the chemical production, pesticide and fertilizer were widely used, and the heavy metal pollution of soil and water was more and more serious. For it would accumulate through natural food chain to affect human health, it is important to carry through the remediation of the heavy metal pollution. But traditional remediation technologies of heavy metal pollution were expensive and would disturb the soil configuration. So as a kind of newly invented phytoremediation that has advantage of low cost and no secondary pollution could be widely applied. For Pb tolerance mechanism was lessly knowed, the application of phytoremediation was geeatly limited.In this paper, tow Pb hypertolerant plants were experimented by Pb stress to probe into Pb torelance mechanism for the application of remediation on Pb pollution of soil. On the method of water culture, the accumulation ability of the two plans was study. And Pb content in plants was determined by atom absorption spectrophotometer; the difference of Pb chemical form in plants under the Pb stress was studied by stepwise extraction; the relation between nonprotein thiols and Pb stress was studied on the method of DTNB; the distribution of Pb in plants in cell level was analyzed through electron microscope. The main results obtained were summarized as follows:1. The experiment results showed: Pb content in the two plants was more and more when the treatment concentration added. When the treatment concentration was 750mg/L, the Pb content in the root and leaf of Pogonatherum Crinitum were the most, that was 4639.4±613.9 mg/kg and 5467.2±925.5 mg/kg; And when the treatment concentration was 1000mg/L, the Pb content in the root and leaf of Isachne globosa were the most, that was 9034.6±1125.3mg/kg and 6828.4±773.5 mg/kg. So Pogonatherum Crinitum and Isachne globosa with great accumulation ability could be used for heavy metal pollution remediation.2. Along with Pb treatment concentration adding, the content of Pb in HCl extraction, acetic acid extraction, ethanol extraction and NaCl extraction were all higher in the root of Pogonatherum Crinitum, and HCl extraction increased the most, form 30.39% to 46.84%; Ethanol extraction was from 14.15% to 21.63%; acetic acid extraction was from 15.02% to 21.04%; NaCl extraction was from 8.43 % to 22.56%. And the Pb content of residual state and water soluble state were from 4.23% to 9.99% and from 3.61% to 8.07%. Along with Pb treatment concentration adding, the Pb content of HC1 extraction, acetic acid extraction, was higher in the leaf of Pogonatherum Crinitum. And HC1 extraction increased the most of all, was the dominant Pb chemical form in the leaf of Pogonatherum Crinitum. Its average was 45.49% and it even come to 61.49% at the level of 50mg/L Pb treatment.And the Pb content of all form in the root of Isachne globosa was the most in HC1 extraction, and then acetic acid extraction took second place; NaCl extraction and ethanol extraction were the third; residual state and water soluble state were the least. And the Pb content of all form in the leaf of Isachne globosa was the most in HC1 extraction; acetic acid extraction, NaCl extraction and ethanol extraction took the second place; water soluble and residual state state were the least.3.Under the different concentration of Pb stress, the content of nonprotein thiols in the leaf and root of Pogonatherum Crinitum and Isachne globosa increased. But the difference between in leaf and root was not significant. The Correlation analysis of Pb stress and nonprotein thiols showed nonprotein thiols could not be biological index of Pb stress.4.The distributing of Pb in the two plants in the cell level was studied by transmission electron microscope. There was no black Pb precipitate pellets in the photograph of the leaf and root of Pogonatherum Crinitum control group. But in the photograph of the leaf and root of Pogonatherum Crinitum treatment group there was, especially in cell wall. The situation in Isachne globosa was the same as Pogonatherum Crinitum.5. Malic acid and Citric acid in the leaf of Pogonatherum Crinitum and Isachne globosa had extremely correlation with Pb stress. The correlation coefficient of Citric acod was 0.9627 and 0.8579, but Acetic acid was -0.0735 and -0.0304. So Malic acid and Citric acid maybe one of Pb tolerance Mechanism of the two plants, but Acetic acid and oxalic acid were not the one.