硝磺草酮、铜单一和复合胁迫对苦草的生长及生理的影响

Effect of single and combined stress of mesotrione and copper on the growth and physiology of Vallisneria natans

农药与重金属是水体中常见的污染物,其在水环境中的污染问题已引起全社会的广泛关注。目前关于农药硝磺草酮与铜的研究主要集中在动物与浮游植物上,对大型水生植物的研究较匮乏。为了阐明水体中常见毒性污染物硝磺草酮与铜对水生植物的潜在毒性作用,本研究探究了二者对长江流域的优势种苦草(Vallisneria natans)的生长及生理影响,旨在为水生植物复合污染的生态毒性效应和生态安全评估提供依据。本研究采用水培法,研究了不同浓度硝磺草酮(0、0.01、1、10、20、50 mg/L)、铜(0、0.1、0.3、0.5、1、2 mg/L)以及(硝磺草酮+铜)在(0+0、0.01+0.1、1+0.3、10+0.5、20+1、50 mg/L+2 mg/L)浓度时对苦草的相对生长率、光合色素(叶绿素a、叶绿素b、类胡萝卜素)、抗氧化酶〔超氧化物歧化酶(superoxide dismutase,SOD)、过氧化物酶(peroxidase,POD)、过氧化氢酶(catalase,CAT)〕以及可溶性蛋白含量变化的影响。结果显示,单一硝磺草酮对苦草的生长和光合色素的合成、CAT活性和可溶性蛋白含量具有抑制作用,而对苦草POD活性具有激活效应;单一铜胁迫对苦草生长、光合色素的合成、CAT活性以及可溶性蛋白含量具有显著抑制作用,而对苦草SOD和POD活性具有激活效应;此外,苦草的相对生长率、光合色素、可溶性蛋白含量、CAT活性等指示物对硝磺草酮与铜联合胁迫表现出受害响应,而POD活性显著上升,SOD活性呈现低浓度抑制高浓度促进效应。毒性效应评估结果显示,随着复合胁迫浓度的升高,硝磺草酮和铜对苦草的联合毒性由拮抗作用转为协同作用。硝磺草酮与铜在水体中赋存可能对水生植物产生潜在的生物安全风险,因此要更加关注水体中不同污染物之间综合效应的防治。

Pesticides and heavy metals are common pollutants in water.Their pollution in the water has aroused widespread concern in the whole society.At present,the researches on the mesotrione and copper focus on animals and phytoplankton,and the researches on large aquatic plants are scarce.In order to elucidate the potential toxic effects of com⁃mon aquatic pollutants,mesotrione and copper,on aquatic plants,this study investigated their impact on the growth and physiological responses of Vallisneria natans,a dominant species in the Yangtze River basin.The aim was to provide in⁃sights for the ecological toxicity effects and ecological safety assessment of compound pollution on aquatic plants.Hydro⁃ponic experiments were conducted to assess the effects of different concentrations of mesotrione(0.01,1,10,20,50 mg/L),copper(0.1,0.3,0.5,1,2 mg/L),and(mesotrione+copper)(0+0,0.01+0.1,1+0.3,10+0.5,20+1,50 mg/L+2 mg/L)on Vallisneria natans.Parameters studied included relative growth rate(RGR),photosynthetic pigments(chlorophyll a,chlorophyll b,carotenoids),antioxidant enzymes(SOD,POD,CAT),and soluble protein content.Mesotrione exhibited inhibitory effects on the growth and photosynthetic pigment synthesis,CAT activity,and soluble protein content in Vallisneria natans,while activating POD activity.Single copper stress significantly inhibited growth,photosynthetic pigment synthesis,CAT activity,and soluble protein content,while activating SOD and POD activities.The combined stress of mesotrione and copper induced adverse responses in terms of RGR,photosynthetic pig⁃ments,soluble protein content,and CAT activity in Vallisneria natans.Notably,POD activity increased significantly,whereas SOD activity displayed a concentration⁃dependent inhibitory effect at low concentrations and a stimulating effect at high concentrations.Toxicity assessment revealed that with an increase in the concentration of combined stress,the joint toxicity of mesotrione and copper shifted from antagonistic effect to synergistic effect.The coexistence of mesotrione and copper in aquatic ecosystems may pose potential biological risks to aquatic plants.Therefore,greater attention should be paid to the prevention and control of the combined effects of different pollutants in aquatic environments.