诺氟沙星对芽期玉米的毒性和氧化损伤研究

畜禽养殖废弃物的农田处置,使大量抗生素进入环境,从而对环境生物产生潜在危害.为了研究诺氟沙星(norfloxacin,Nor)对玉米发芽和幼苗生长的影响,采用水培发芽实验,测定了不同浓度下,诺氟沙星对玉米种子的发芽率和玉米幼苗对诺氟沙星的吸收与传输的影响;另外还研究了诺氟沙星对玉米幼苗生物量、自由基水平、丙二醛(MDA)含量、抗氧化酶活性的影响.结果显示,诺氟沙星能被玉米根吸收并传输到地上部分.0.5mg·L-1～50mg·L-1的诺氟沙星暴露均不影响玉米的发芽率.当诺氟沙星浓度大于1mg·L-1时,幼苗的生长受到抑制,其敏感指标依次为根重>根长>芽长>芽重.诺氟沙星暴露使玉米根、芽中MDA含量明显增加,玉米根中谷胱甘肽硫转移酶(GST),过氧化物酶(POD),超氧化物歧化酶(SOD)和过氧化氢酶(CAT)等抗氧化酶的活度有显著改变,这表明诺氟沙星暴露能够引起玉米体内的氧化损伤.用电子自旋共振结合二级自由基自旋捕获技术测定了玉米根中自由基水平,发现诺氟沙星能够引起玉米根中大量羟基自由基的产生,为诺氟沙星引起玉米幼苗的氧化损伤提供了直接的证据.

Phytotoxicity and Oxidative Stress of Norfloxacin on Maize(Zea mays L.)Germination Stage

Land application of manure waste leads to an increasing level of antibiotics in the environment and constitute a potential damage to ecological systems.Germination test was conducted to investigate the toxicity of norfloxacin(Nor)on maize(Zea mays L.)germination and seedling growth.Germination rate,seedling biomass,Nor uptake and transportation,free radical level,lipid peroxidation products,and antioxidative enzyme activities were determined under exposure of Nor with different concentrations.The results show that Nor could be taken up by maize root and transported to shoot.0.5mg·L-1~50mg·L-1 of Nor did not affect germination rate.Maize growth was inhibited when Nor concentration was higher than 1mg·L-1 and the susceptibility of the tested endpoints followed the order:root fresh weight>root length>shoot height>shoot fresh weight.Lipid peroxide malonaldehyde(MDA)in both root and shoot increased with Nor concentration increasing.Activity of antioxidative enzymes,glutathione s-transferase(GST),catalase(CAT),peroxidase(POD)and superoxide dismutase(SOD)in root changed significantly.All the results show an oxidative stress on the body of maize caused by Nor.Furthermore,large amount of free radicals in root detected using an secondary spin trapping/electron paramagnetic resonance(EPR)method had been found,which provide a direct evidence for oxidative damage on maize seedling caused by Nor.