芘胁迫对5种羊茅属植物根系分泌的几类低分子量有机物的影响
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摘要
根系分泌物与有机污染物的植物修复过程密切相关,研究胁迫条件下不同修复潜力植物根系分泌物的释放特征有助于揭示植物修复的内在机制.借助根际袋土培试验研究了芘胁迫(10~160 mg·kg~(-1))下5种羊茅属植物在不同胁迫期(30~70d)时根系分泌物中几种低分子量有机物的释放特征.结果表明:1芘胁迫促进了根系对可溶性糖的分泌:随着胁迫水平的升高、胁迫期的延长,其分泌量呈"先升后降"变化趋势,胁迫水平为C3(40.36 mg·kg~(-1))、胁迫期为40 d时达到最大值;修复潜力越大,趋势越明显.2芘胁迫增强了根系对低分子量有机酸的释放,修复潜力越大,释放高峰值出现时的胁迫浓度越高,且主要以草酸、乙酸、乳酸和苹果酸为主(>98.15%),但修复潜力较强物种的根系分泌物中也检测到微量反丁烯二酸.3芘胁迫对氨基酸的种类影响不大,但对分泌量影响较大:苏氨酸、丝氨酸、甘氨酸、丙氨酸的分泌量随着胁迫水平的升高而剧增;脯氨酸、羟脯氨酸和天冬氨酸对芘胁迫的响应近乎以功能群的形式参与植物修复过程,参与的组分越多,修复潜力越强.可见,芘胁迫下根系分泌物中可溶性糖、低分子量有机酸以及氨基酸的释放特征与植物自身的修复潜力有关;修复潜力越强,释放量越多且成分越复杂,并表现出更强的环境适应性及生理可塑性.
Phytoremediation is an important measure to remove organic pollutants from contaminated soil,and the root secretion of plant is considered to be closely related to the mechanisms of phytoremediation of organic pollutants. It is in favor of revealing the mechanisms of remediation by studying the characteristics of root exudates of plants with phytoremediation potential under the stress of pollutants. In the present research,pyrene and five species of Festuca which have been testified to be tolerant to pyrene stress were selected as studied objects. A soil~-cultivating experiment with rhizobag technique was conducted to investigate the effects of pyrene on low molecule weight organic compounds in the root exudates of plant species under five concentration levels of pyrene( 10. 19,20. 32,40. 36,79. 94,and 160. 68 mg·kg~(-1),denoted by C1,C2,C3,C4 and C5,respectively) on day 30,40,50,60 and 70 of experiments. The results showed that the presence of vegetation significantly enhanced the dissipation of pyrene in the soil environment.This effect was especially marked with Festuca arundinacea,followed by those with Festuca mazzetiana,Festuca pubiglumis,and Festuca longiglumis,and that with Festuca stapfii was the lowest. During the whole experiments,the amounts of soluble sugar excreted by the five species of Festuca tested in root exudates were promoted with pyrene stress,then fluctuated with a stable trend along with the increase of stress concentration or the extension of stress period,which appeared to rise appreciably at relative low pyrene spiked( C1-C3) or earlier stress stage( 30-40 d) and reduce at relative high pyrene spiked level( C3-C5) or later stress stage( 40-70 d),and the highest amount of soluble sugars in root exudates occurred on day 50 of experiments with 40. 36 mg·kg~(-1)pyrene treatment. The greater the phytoremediation potential of the plant species tested,the more obvious this trend wads. Compared with the control treatment( CK),pyrene stress promoted the root system of all five species of Festuca tested to release more low molecular weight organic acids,the stronger the restoration potential of plant species,the higher the concentration of pyrene stress under which the amount of organic acids in root exudates was increased to the peak value. Among the five species of Festuca tested,oxlic acid,acetic acid,lactic acid and malic acid were the main components of organic acids in root exudates,with a percentage of greater than 98. 15% in all pyrenestress treatments,but there were traces of fumaric acid in the roots secretion of plant species with the stronger restoration potential.Data also indicated that 19 types of amino acids were found in root exudates of Festuca and the composition of amino acids in root exudates of Festuca was stable under all pyrene stress treatments,but the amino acid amount was different in root exudates under pyrene stress. The amount of all amino acids in those root exudates increased with increasing pyrene concentration,especially,the amount of threonine,serine,glycine,and alanine increased significantly among the 19 types of amino acids and the differences were significant among different treatments with different pyrene concentrations( P < 0. 05). However,proline,hydroxy proline and aspartic acid were always released in the form of functional group as a response to the pyrene stress,their contents soared quickly with the increase of stress concentration in soils,and the difference was significant among different treatments with different pyrene concentrations( P <0. 05); the more the components of functional group participated in stress response,the stronger the restoration potential of plant species. These results indicated secretion characteristics of soluble sugar,low molecular weight organic acids and amino acids in the root system were closely related to their phytoremediation potential under the pyrene stress,the greater the phytoremediation potential,the more the amount of these low molecular weight secretions and the more complex these components,and the stronger the adaptability to polluted environment and the physiological plasticity to adapt to these contaminants.
Phytoremediation is an important measure to remove organic pollutants from contaminated soil,and the root secretion of plant is considered to be closely related to the mechanisms of phytoremediation of organic pollutants. It is in favor of revealing the mechanisms of remediation by studying the characteristics of root exudates of plants with phytoremediation potential under the stress of pollutants. In the present research,pyrene and five species of Festuca which have been testified to be tolerant to pyrene stress were selected as studied objects. A soil~-cultivating experiment with rhizobag technique was conducted to investigate the effects of pyrene on low molecule weight organic compounds in the root exudates of plant species under five concentration levels of pyrene( 10. 19,20. 32,40. 36,79. 94,and 160. 68 mg·kg~(-1),denoted by C1,C2,C3,C4 and C5,respectively) on day 30,40,50,60 and 70 of experiments. The results showed that the presence of vegetation significantly enhanced the dissipation of pyrene in the soil environment.This effect was especially marked with Festuca arundinacea,followed by those with Festuca mazzetiana,Festuca pubiglumis,and Festuca longiglumis,and that with Festuca stapfii was the lowest. During the whole experiments,the amounts of soluble sugar excreted by the five species of Festuca tested in root exudates were promoted with pyrene stress,then fluctuated with a stable trend along with the increase of stress concentration or the extension of stress period,which appeared to rise appreciably at relative low pyrene spiked( C1-C3) or earlier stress stage( 30-40 d) and reduce at relative high pyrene spiked level( C3-C5) or later stress stage( 40-70 d),and the highest amount of soluble sugars in root exudates occurred on day 50 of experiments with 40. 36 mg·kg~(-1)pyrene treatment. The greater the phytoremediation potential of the plant species tested,the more obvious this trend wads. Compared with the control treatment( CK),pyrene stress promoted the root system of all five species of Festuca tested to release more low molecular weight organic acids,the stronger the restoration potential of plant species,the higher the concentration of pyrene stress under which the amount of organic acids in root exudates was increased to the peak value. Among the five species of Festuca tested,oxlic acid,acetic acid,lactic acid and malic acid were the main components of organic acids in root exudates,with a percentage of greater than 98. 15% in all pyrenestress treatments,but there were traces of fumaric acid in the roots secretion of plant species with the stronger restoration potential.Data also indicated that 19 types of amino acids were found in root exudates of Festuca and the composition of amino acids in root exudates of Festuca was stable under all pyrene stress treatments,but the amino acid amount was different in root exudates under pyrene stress. The amount of all amino acids in those root exudates increased with increasing pyrene concentration,especially,the amount of threonine,serine,glycine,and alanine increased significantly among the 19 types of amino acids and the differences were significant among different treatments with different pyrene concentrations( P < 0. 05). However,proline,hydroxy proline and aspartic acid were always released in the form of functional group as a response to the pyrene stress,their contents soared quickly with the increase of stress concentration in soils,and the difference was significant among different treatments with different pyrene concentrations( P <0. 05); the more the components of functional group participated in stress response,the stronger the restoration potential of plant species. These results indicated secretion characteristics of soluble sugar,low molecular weight organic acids and amino acids in the root system were closely related to their phytoremediation potential under the pyrene stress,the greater the phytoremediation potential,the more the amount of these low molecular weight secretions and the more complex these components,and the stronger the adaptability to polluted environment and the physiological plasticity to adapt to these contaminants.
引文
[1]母清林,方杰,邵君波,等.长江口及浙江近岸海域表层沉积物中多环芳烃分布、来源与风险评价[J].环境科学,2015,36(3):839-846.
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[8]潘声旺,魏世强,袁馨,等.蚯蚓活动对金发草修复土壤菲芘污染的强化作用[J].土壤学报,2011,48(1):62-70.
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[10]Bertin C,Yang X H,Weston L A.The role of root exudates and allelochemicals in the rhizosphere[J].Plant and Soil,2003,256(1):67-83.
[11]Marschner H,Rmheld V,Cakmak I.Root-induced changes of nutrient availability in the rhizosphere[J].Journal of Plant Nutrition,1987,10(9-16):1175-1184.
[12]Susarla S,Medina V F,Mc Cutcheon S C.Phytoremediation:an ecological solution to organic chemical contamination[J].Ecological Engineering,2002,18(5):647-658.
[13]Gao Y Z,Ren L L,Ling W T,et al.Desorption of phenanthrene and pyrene in soils by root exudates[J].Bioresource Technology,2010,101(4):1159-1165.
[14]Zhu Y H,Zhang S Z,Huang H L,et al.Effects of maize root exudates and organic acids on the desorption of phenanthrene from soils[J].Journal of Environmental Sciences,2009,21(7):920-926.
[15]Luo L,Zhang S Z,Shan X Q,et al.Oxalate and root exudates enhance the desorption of p,p'-DDT from soils[J].Chemosphere,2006,63(8):1273-1279.
[16]Kirk J L,Klironomos J N,Lee H,et al.The effects of perennial ryegrass and alfalfa on microbial abundance and diversity in petroleum contaminated soil[J].Environmental Pollution,2005,133(3):455-465.
[17]Khan S,Afzal M,Iqbal S,et al.Plant-bacteria partnerships for the remediation of hydrocarbon contaminated soils[J].Chemosphere,2013,90(4):1317-1332.
[18]许超,林小方,夏北成.玉米幼苗根系分泌物对芘污染的响应[J].生态学报,2010,30(12):3280-3288.
[19]谢晓梅,廖敏,杨静.芘对黑麦草根系几种低分子量有机分泌物的影响[J].生态学报,2011,31(24):7564-7570.
[20]Yi H,Crowley D E.Biostimulation of PAH degradation with plants containing high concentrations of linoleic acid[J].Environmental Science&Technology,2007,41(12):4382-4388.
[21]张晶,林先贵,刘魏魏,等.土壤微生物群落对多环芳烃污染土壤生物修复过程的响应[J].环境科学,2012,33(8):2825-2831.
[22]吴林坤,林向民,林文雄.根系分泌物介导下植物-土壤-微生物互作关系研究进展与展望[J].植物生态学报,2014,38(3):298-310.
[23]Krumins J A,Goodey N M,Gallagher F.Plant-soil interactions in metal contaminated soils[J].Soil Biology and Biochemistry,2015,80:224-231.
[24]沈宏,严小龙,郑少玲,等.铝毒胁迫诱导菜豆柠檬酸的分泌与累积[J].应用生态学报,2002,13(3):307-310.
[25]Shahzad T,Chenu C,Genet P,et al.Contribution of exudates,arbuscular mycorrhizal fungi and litter depositions to the rhizosphere priming effect induced by grassland species[J].Soil Biology and Biochemistry,2015,80:146-155.
[2]姚林林,张彩香,李佳乐,等.污灌区土壤中多环芳烃的垂直分布及可能来源[J].环境科学,2013,34(4):1553-1560.
[3]Mueller K E,Shann J R.PAH dissipation in spiked soil:impacts of bioavailability,microbial activity,and trees[J].Chemosphere,2006,64(6):1006-1014.
[4]Joner E J,Leyval C.Rhizosphere gradients of polycyclic aromatic hydrocarbon(PAH)dissipation in two industrial soils and the impact of arbuscular mycorrhiza[J].Environmental Science&Technology,2003,37(11):2371-2375.
[5]Kim Y B,Park K Y,Chung Y,et al.Phytoremediation of anthracene contaminated soils by different plant species[J].Journal of Plant Biology,2004,47(3):174-178.
[6]Gao Y Z,Ling W T,Wong M H.Plant-accelerated dissipation of phenanthrene and pyrene from water in the presence of a nonionic-surfactant[J].Chemosphere,2006,63(9):1560-1567.
[7]Wei S Q,Pan S W.Phytoremediation for soils contaminated by phenanthrene and pyrene with multiple plant species[J].Journal of Soils and Sediments,2010,10(5):886-894.
[8]潘声旺,魏世强,袁馨,等.蚯蚓活动对金发草修复土壤菲芘污染的强化作用[J].土壤学报,2011,48(1):62-70.
[9]Phillips L A,Greer C W,Farrell R E,et al.Plant root exudates impact the hydrocarbon degradation potential of a weatheredhydrocarbon contaminated soil[J].Applied Soil Ecology,2012,52:56-64.
[10]Bertin C,Yang X H,Weston L A.The role of root exudates and allelochemicals in the rhizosphere[J].Plant and Soil,2003,256(1):67-83.
[11]Marschner H,Rmheld V,Cakmak I.Root-induced changes of nutrient availability in the rhizosphere[J].Journal of Plant Nutrition,1987,10(9-16):1175-1184.
[12]Susarla S,Medina V F,Mc Cutcheon S C.Phytoremediation:an ecological solution to organic chemical contamination[J].Ecological Engineering,2002,18(5):647-658.
[13]Gao Y Z,Ren L L,Ling W T,et al.Desorption of phenanthrene and pyrene in soils by root exudates[J].Bioresource Technology,2010,101(4):1159-1165.
[14]Zhu Y H,Zhang S Z,Huang H L,et al.Effects of maize root exudates and organic acids on the desorption of phenanthrene from soils[J].Journal of Environmental Sciences,2009,21(7):920-926.
[15]Luo L,Zhang S Z,Shan X Q,et al.Oxalate and root exudates enhance the desorption of p,p'-DDT from soils[J].Chemosphere,2006,63(8):1273-1279.
[16]Kirk J L,Klironomos J N,Lee H,et al.The effects of perennial ryegrass and alfalfa on microbial abundance and diversity in petroleum contaminated soil[J].Environmental Pollution,2005,133(3):455-465.
[17]Khan S,Afzal M,Iqbal S,et al.Plant-bacteria partnerships for the remediation of hydrocarbon contaminated soils[J].Chemosphere,2013,90(4):1317-1332.
[18]许超,林小方,夏北成.玉米幼苗根系分泌物对芘污染的响应[J].生态学报,2010,30(12):3280-3288.
[19]谢晓梅,廖敏,杨静.芘对黑麦草根系几种低分子量有机分泌物的影响[J].生态学报,2011,31(24):7564-7570.
[20]Yi H,Crowley D E.Biostimulation of PAH degradation with plants containing high concentrations of linoleic acid[J].Environmental Science&Technology,2007,41(12):4382-4388.
[21]张晶,林先贵,刘魏魏,等.土壤微生物群落对多环芳烃污染土壤生物修复过程的响应[J].环境科学,2012,33(8):2825-2831.
[22]吴林坤,林向民,林文雄.根系分泌物介导下植物-土壤-微生物互作关系研究进展与展望[J].植物生态学报,2014,38(3):298-310.
[23]Krumins J A,Goodey N M,Gallagher F.Plant-soil interactions in metal contaminated soils[J].Soil Biology and Biochemistry,2015,80:224-231.
[24]沈宏,严小龙,郑少玲,等.铝毒胁迫诱导菜豆柠檬酸的分泌与累积[J].应用生态学报,2002,13(3):307-310.
[25]Shahzad T,Chenu C,Genet P,et al.Contribution of exudates,arbuscular mycorrhizal fungi and litter depositions to the rhizosphere priming effect induced by grassland species[J].Soil Biology and Biochemistry,2015,80:146-155.