Study On Uptake Mechanism And Molecular Speciation Of Copper In Elsholtzia Splendens And Commelina Communis

Cu is a heavy metal, fully used but harmful for people's health. It is one of major element in our country's contaminated soil, especially in Jiangxi and Zhejiang province. E. splendens and C. communis were reported as copper-accumulated plants, which were benefit for phytoremediation of Cu-contaminated soil. However, the mechanism of Cu accumulation needed for further research. In this paper, we compared the Cu uptake way with these two plants and the relationship between Cu uptake and the root Fe(III)-chelate reductase (FCR) activity, studied the characters of Cu and other elements distribution using synchrotron radiation X-ray fluorescence spectroscopy (SRXRF), investigated Cu molecular speciation and its transformation with X-ray absorption spectroscopy (XAS), and then separated the Cu-binding proteins. The purpose of our study was to clarify the mechanism of Cu uptake and accumulation in E. splendens and C. communis, which could provid theory basis for phytoremediation. The main results were as follows:The results showed heavy metals in contaminated soil could be activated by root exudates of E. splendens and C. communis, and there was no significant difference among the root exudates with control, high Cu Fe deficiency and Zn deficiency treatment. There organic acid in the root exudates was different among different treatments, but the oxalic acid and an unknown organic acid were dominants. The mobility of Cu and Zn in contaminated soil was improved obviously by P. aeruginosa ZD4-3 and P. Chrysosprim, and the mobility of Pb was improved by P. aeruginosa ZD4-3 while inhibited by P. Chrysosprim. Root exudates of E. splendens inhibited the activation of P. aeruginosa ZD4-3 to heavy metals, while promoted the activation of P. Chrysosprim.The ability of Cu accumulation in E. splendens was higher than in C. communis, but the ability of Cu transport was lower. Both the uncoupler of oxidative phosphorylation DNP and P-type ATPase inhibitor Na3VO4 could inhibit Cu uptake, which showed properly the two plants could uptake Cu initiatively. Ca2+ ion channel inhibitor LaCl3 inhibited Cu uptake of E. splendens while not inhibit Cu uptake of C. communis, which demonstrated Cu uptake of E. splendens was related to Ca2+ ion channel, while Cu uptake of C. communis was not. On the contrary, Cu uptake of C. communis was inhibited by the protein synthesis inhibitor cycloheximide, while Cu uptake of E. splendens was not. Cu uptake was hardly affected byZn deficiency at low Cu, while Cu uptake was promoted at high Cu.The results showed that Cu uptake and accumulation in C. communis and E. splendens was significantly enhanced by Fe deficiency, and the Cu concentration in roots and shoots was increased, then decreased with the time of Fe deficiency treatment. The bioavailability of different Cu speciation, such as EDTA-Cu, NTA-Cu, oxalate-Cu, and citrate-Cu, could be promoted by Fe deficiency. It suggested that there was an inherent relationship between Cu uptake and element Fe. Fe deficiency could acidify the rhizosphere of C. communis. Cu uptake in Fe-deficient plants was still higher than that of Fe-sufficient plants when P-type ATPase inhibitor Na3VO4 was added in the solution, which demonstrated that Fe deficiency induced stimulation of the plasma membrane H+-ATPase did not play a role in the enhanced Cu uptake.Both Fe deficiency and Cu deficiency could induce root FCR activity in C. communis. Cu deficiency could induce root FCR activity in E. splendens, While Fe deficiency not. Both FCR activity and Cu concentration in roots of C. communis inhibited distinctly by cycloheximide, a kind of protein synthesis inhibitor. During the course of Fe deficiency, there simultaneously appeared Cu concentration and FCR activity peaks in roots at day 9. All above evidences demonstrated Cu uptake and accumulation in C. communis were probably related to the root FCR activity.Synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) microprobe was used to study Cu and other elements distribution in E. splendens and C. communis. P...