梭鱼草叶片抗氧化酶、抗坏血酸-谷胱甘肽循环与乙二醛酶系统对铅胁迫的响应

Response of Antioxidase,Ascorbate-Glutathione Cycle and Glyoxalase System in Leaves of Pontederia cordata to Lead Exposure

为了探明梭鱼草叶片细胞应对Pb^(2+)胁迫的生理机制,研究以液培法考察了不同浓度Pb^(2+)胁迫下梭鱼草叶片丙二醛(MDA)与叶绿素含量,以及抗氧化酶活性、抗氧化剂含量和乙二醛酶系统的变化规律。结果表明,(1)5.0 mg/L Pb^(2+)胁迫第14天和第21天时,梭鱼草叶片叶绿素含量,过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)等抗氧化酶活性,抗坏血酸(AsA)、脱氢抗坏血酸(DHA)、谷胱甘肽(GSH)、非蛋白巯基总肽(NPT)和植物螯合肽(PCs)等抗氧化剂含量没有发生明显变化;第21天时叶片细胞中甲基乙二醛(MG)含量显著增加,而MDA含量无明显增加。(2)10.0 mg/L Pb^(2+)处理至第21天时,梭鱼草叶片MDA、MG、GSH及NPT含量及过氧化物酶(POD)活性明显增加,而脱氢抗坏血酸还原酶(DHAR)、甲基乙二醛酶Ⅱ(GlyⅡ)活性呈相反变化趋势。(3)在15.0 mg/L Pb^(2+)处理期间,梭鱼草叶片MDA含量显著增加,其GSH、NPT、PCs被诱导合成以螯合细胞中过量积累的Pb^(2+);同时叶片POD、SOD、APX活性和AsA含量显著增加。15.0 mg/L Pb^(2+)处理第21天时,乙二醛酶系统已经不能缓解高浓度Pb^(2+)胁迫诱发的羰基胁迫。可见,梭鱼草叶片对5.0 mg/L Pb^(2+)具有良好的耐受性;在较高浓度(≥10.0 mg/L)Pb^(2+)胁迫下,梭鱼草叶片细胞膜脂过氧化作用加剧,此时其主要通过合成非蛋白巯基化合物、增加抗氧化酶活性及AsA含量来减缓氧化损伤;本试验条件下梭鱼草叶片乙二醛酶系统没有表现出明显的解毒作用。

To identify the physiological mechanisms in leaves of Pontederia cordata to Pb^(2+)exposure,we adopted a hydroponic experiment to investigate variations in malonaldehyde(MDA)and chlorophyll contents,antioxidase activity,antioxidant content,and glyoxalase system in the plant leaves with 0-15.0 mg/L Pb^(2+)concentration exposure.Results showed that,(1)no obvious variations in chlorophyll content,catalase(CAT),superoxide dismutase(SOD)and ascorbate peroxidase(APX)activities,ascorbic acid(AsA),dehydroascorbic acid(DHA),glutathione(GSH),non-protein thiol total peptide(NPT)and phytochelatins(PCs)contents were detected in the plant leaves with 5.0 mg/L Pb^(2+)exposure for 14 d and 21 d;with 5.0 mg/L Pb^(2+)exposure for 21 d,a marked increase in methylglyoxal(MG)but not MDA content was noticed.(2)With 10.0 mg/L Pb^(2+)exposure for 21 d,MDA,MG,GSH,and NPT contents and meanwhile POD activity in the leaves markedly increased,and an opposite trend was demonstrated in monodehydroascorbate content and glyoxalaseⅡ(GlyⅡ).(3)With the plants exposed with 15.0 mg/L Pb^(2+),MDA content in the leaves significantly increased,and by this time GSH,NPT,PCs were synthesized to chelate excessive Pb^(2+)accumulated in the leaves.And meanwhile,POD,SOD,and APX activities and AsA content were also stimulated to alleviate oxidative damage induced by Pb^(2+).Glyoxalase system cannot effectively cope with carbonyl stress induced by the treatment of 15.0 mg/L Pb^(2+)exposure for 21 d.The leaves of P.cordata exhibited a good tolerance to 5.0 mg/L Pb^(2+)exposure.The stimulated non-protein thiol compound synthesis,antioxidase activity and AsA content were employed to mitigate oxidative damage induced by Pb^(2+)concentrations no less than 10.0 mg/L.Glyoxalase system in leaves of Pontederia cordata did not represent an markedly detoxification as expected under the present experimental condition.