Response Of Hydrilla Verticillata To The Stress Of Lead And Zinc And Studies On Its Metabolomics

Heavy metal pollutants in waters are one of the global environmental concerns,and its harms on the livings and the plants'function of improving the environment have received considerable critical attention.The main purpose of this study is to develop an understanding of Hydrilla verticillata,which plays an important role in water restoration,based on the stress factors of lead and zinc.According to the standard concentrations of lead and zinc in Class?,Class?,Class?,and the exceeded standard of concentration value of Class?in the"Environmental Quality Standards of Surface Water"(GB 3838-2002),different concentrations of lead stress and zinc stress were handled.After 28 days'stress treatments for Hydrilla verticillata,the contents of lead,zinc,chlorophyll,MDA and antioxidant system in the Hydrilla verticillata were studied,and we alsostudy the characteristics of the primary metabolites by selecting experimental groups treated with lead stress,zinc stress or lead-zinc stress according to their concentration values in Class?and the exceeded standard of concentration value of Class?.Overall,these finding provide basic data of biological toxicity and the restoration of heavy metal-polluted waters.The main results are as follows:1.The adsorption of lead by Hydrilla verticillata under lead stress and lead-zinc stressUnder the condition of lead stress,the content of lead in Hydrilla verticillata also increased with the increasing of the concentration of Pb²⁺.when the Pb²⁺concentration was 0.20mg/L,there is a significant increase of 174.28%(P<0.05)than that in 0.10mg/L.Compared with groups under lead stress,the groups under the lead-zinc stress that the content of lead in Hydrilla verticillata were increased with the increasing of the concentrations,in which,at the same Pb²⁺concentrations,the zinc content rised significantly with the increase of the Zn²⁺concentrations(P<0.05);at the group with same Zn²⁺concentrations,the lead content was also increased significantly with the increasing of the Pb²⁺concentrations(P<0.05).2.The adsorption of zinc by Hydrilla verticillata under zinc and lead-zinc stress.Under the zinc stress,the content of zinc in Hydrilla verticillata also increased with the increasing of Zn²⁺concentration;when Zn²⁺concentration was 1.00mg/L,there was a significant increase of 1036.03%(P<0.05)compared to that in 0.05mg/L.and when Zn²⁺concentration was 4.00mg/L,the content reached a maximum value of3417.71±396.77mg/kg.Compared with groups under lead stress,the groups under the lead-zinc stress that the content of zinc in the Hydrilla verticillata were increased with the increasing of the concentrations,in which,at the same Zn²⁺concentrations and when the Zn²⁺concentration was 4.00mg/L,the content of zinc in Hydrilla verticillata treated with lead-zinc stress was increased more significantly than that only treated with zinc stress(P<0.05);at the same Pb²⁺concentrations,the content of zinc was increased significantly with the increase of the Zn²⁺concentrations(P<0.05).3.Physiological and biochemical characteristics of Hydrilla verticillata under the lead stress,zinc stress and lead-zinc stress.Under the lead stress or zinc stress,the content of chlorophyll a and chlorophyll b in the Hydrilla verticillata were showed the variation tendency of falling after rising with the increasing of concentrations.when the Pb²⁺concentration was 0.01mg/L or0.05mg/L and the Zn²⁺concentration was 0.05mg/L,the content of chlorophyll was increased;while the Pb²⁺concentration was 0.10mg/L or 0.20mg/L and the Zn²⁺concentration is 1.00mg/L or higher than 1.00 mg/L,chlorophyll was significantly lower than that in blank control group(P<0.05).From above,it showed that relatively lower concentrations can increase the content of chlorophyll while the relatively higher will inhibit.However,it was found in groups treated with the lead stress or zinc stress that the contents or activities of MDA,T-AOC,SOD,POD,GSH and Pro were significantly higher than those in the blank control group(P<0.05).At the same Pb²⁺concentrations,when the Zn²⁺concentrations reached 1.00mg/L or above,the chlorophyll,MDA and POD activity in the groups treated with lead-zinc stress were significantly lower than that those in the corresponding groups only treated with lead stress(P<0.05),while the activities of the T-AOC and SOD were significantly higher than that of corresponding only treated with lead stress(P<0.05).At the same Zn²⁺concentration,when the Pb²⁺concentration was 0.01mg/L,the contents of chlorophyll and MDA in the groups treated with lead-zinc stress were significantly higher than that of the corresponding groups only treated with zinc stress(P<0.05);when Zn²⁺concentration was 0.05mg/L or 1.00mg/L,the T-AOC of Hydrilla verticillata treated with lead-zinc stress was significantly higher than that corresponding only treated with zinc stress(P<0.05),while T-AOC,POD activity and GSH were significantly lower than that of corresponding groups only treated with zinc stress(P<0.05),when Zn²⁺concentration was 0.05mg/L or 1.00mg/L.4.Primary metabolites of Hydrilla verticillata under lead stress,zinc stress and lead-zinc stressFrom Hydrilla verticillata,342 primary metabolites,including amino acids,nucleotides,organic acids,vitamins,lipids and sugars,were found.Compared with the blank control group,the Pb0.10 and Pb0.20 treatment groups had 11 identical differential metabolites,which was mainly manifested by an increase of phenolic acids and carbohydrate and a decrease of lipid;again,the Zn2.00 and Zn4.00 treatment groups had 65 identical differential metabolites,mainly manifested by an increase of the metabolites,such as amino acids,nucleotides,sugars and organic acids,and a decrease of some phenolic acids and lipids.Compared with Pb0.10 and Pb0.20 groups only treated with lead stress,the Pb0.10+Zn2.00 and Pb0.20+Zn4.00 groups treated with lead-zinc stress had 45 identical differential metabolites,mainly represented by an increase of the amino acids,sugar organic acids and lipid,and a decrease of some phenolic acids,vitamins and lipid.The same differential metabolites were not found in the groups treated with zinc stress at Zn2.00 and Zn4.00 and their corresponding groups treated with lead-zinc stress at Pb0.10+Zn2.00 and Pb0.20+Zn4.00.Moreover,it was found from further comparisons and analyses that treatments with lead-zinc stress can further promote the Pb²⁺'s effect of increasing carbohydrates in Hydrilla verticillata;under high concentration stress(Pb0.10+Zn2.00),treatments with lead-zinc stress can further promote the Zn²⁺'s effect of increasing the nucleotides and organic acid,while it will inhibit Zn²⁺'s effect of reducing the phenolic acids and lipids;under ultra-high concentration stress(Pb0.20+Zn4.00),treatments with lead-zinc stress can inhibit the Zn²⁺'s effect of increasing amino acids and nucleotides and of reducing phenolic acids.It was also found that Phenylacetyl-L-glutamine,L-Tyramine,p-coumaroylcaffeoyltartaric,Glucogallin and Isosalicylic acid O-glycoside can be regarded as the metabolism markers of lead;and the metabolism markers of zinc are5-Aminovaleric acid,L-(+)-Arginine and L-Pyroglutamic Acid cet.