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人类的生存环境离不开地表水体和土壤,然而,由于工业化进程的加速,有害物质的种类和数量急剧增加,破坏生态平衡,且易通过食物链的富集作用危及人类健康。多环芳烃(PAHs)具有难降解性、毒性(致癌、致突变、致畸效应)和生物蓄积性[1-2],是各国优先控制的一类污染物,美国国家环保局(EPA)将萘、菲、芘、苯并[α]芘等16种PAHs列为优先控制污染物[3]。在中国东部109个农业土壤点收集的表层土壤样本中,PAHs的总浓度从8.8到3 880 μg·kg−1不等[4]。菲是三环的PAHs类,主要来源于焦化厂、炼油厂等企业生产的废水、废气及汽车的尾气排放、垃圾焚烧等,是PAHs的代表,通常在土壤、水体和沉积物中的含量较高。
植物修复是一种利用根系和地上部分修复污染土壤和沉积物的低成本修复技术,近年来得到了广泛的研究;但目前植物修复多环芳烃的研究多以草本植物为主,而木本植物具有生物量大、根系发达及地上部分可多年生长等优点。生长较快的洋白蜡(Fraxinus pennsylvanica Marsh.)、DN 34杨(Populus deltoides Marsh.×P. nigra L. DN 34)和黑柳(Salix nigra Marsh.)相比,黑柳对土壤中PAHs的降解率最高[5]。Hultgren等[6]温室实验表明,蒿柳(Salix viminalis L.)种植土壤中菲和芘的降解率分别是没有植物存在的1.47倍和1.27倍。
植物在修复PAHs的过程中,应能承受由污染物引起的胁迫,但高浓度PAHs对植物具有毒害作用,导致其形态学、细胞学以及代谢紊乱[7],甚至死亡[8]。活性氧(ROS)是逆境下破坏植物防御系统,使细胞中毒死亡的重要因素,而抗氧化系统(AOS)在活性氧的清除中起重要作用,常被用于植物的抗性评价[9]。关于植物对PAHs胁迫活性氧生成及抗氧化反应的研究有少量报道,如Salehi-Lisar等[10]用芴处理小麦(Triticunt aestivum L.)、紫花苜蓿(Medicago sativa L.)和向日葵(Helianthus annuus L.),认为过氧化氢酶(CAT)是植物抵御胁迫的重要酶。Weisman等[11]研究表明,PAHs可诱导拟南芥(Arabidopsis thaliana L.)的谷胱甘肽-S-转移酶(GST)活性增加。Shen等[7]认为,类胡萝卜素和超氧化物歧化酶(SOD)是菲胁迫下参与活性氧清除的最有效的抗氧化剂。这些报道表明了抗氧化系统和PAHs之间的关系,但关于木本植物这方面的研究未见报道,而揭示植物膜脂过氧化的原因及关键抗氧化剂的响应是提高植物在PAHs污染环境中抗性的关键。因此,本研究以蒿柳为研究对象,通过前期浓度筛选试验得出其在1.0 mg·L−1菲处理下,植物的生长及根系生理指标受到显著影响,因此,研究该浓度下抗氧化系统的响应,为提高木本植物在PAHs胁迫下的抗性及加强修复效应的研究奠定基础。
菲胁迫下蒿柳抗氧化系统的响应
Response of Antioxidant System of Salix viminalis under Phenanthrene Stress
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摘要:
目的 研究菲胁迫下活性氧和抗氧化物质的变化规律,探究蒿柳抗氧化系统的防御机制,为提高其对多环芳烃(PAHs)的抗性及加强植物修复的研究提供理论依据。 方法 以蒿柳扦插苗为试验材料,采用水培方式,研究其在0、1.0 mg·L−1菲处理下活性氧、抗氧化酶、抗氧化剂以及丙二醛(MDA)的动态变化,处理时间为16 d。 结果 研究表明:(1)菲处理后第4天,H2O2含量和氧自由基(O2·−)生成速率迅速增加,MDA含量升高,过氧化氢酶(CAT)活性显著上升;第8天超氧化物歧化酶(SOD)和过氧化物酶(POD)活性显著升高;第16天时,H2O2含量下降到与对照无显著差异,O2·−和MDA的增加量下降。(2)还原型谷胱甘肽(GSH)和谷胱甘肽还原酶(GR)在处理后第4天即迅速上升,谷胱甘肽-S-转移酶(GST)呈缓慢上升趋势。(3)还原型抗坏血酸(AsA)含量在处理后第4天低于对照,但随着处理时间的延长呈上升趋势,在第16天时高于对照。 结论 菲胁迫下,O2·−是造成细胞膜脂过氧化的主要活性氧,SOD活性一直高于对照,但不足以清除增加的O2·−,CAT和POD的升高可以清除过量的H2O2;GSH是抵御菲胁迫的有效抗氧化剂,并通过GST的催化参与菲的解毒。 Abstract:Objective In order to explore the defense mechanism of the antioxidant system of Salix viminalis , the dynamic changes of reactive oxygen and antioxidant substances under phenanthrene stress were observed which can provide new evidence for improving the resistance of plants to polycyclic aromatic hydrocarbon (PAHs) stress and enhancing the phytoremediation potential. Method The cutting seedlings of S. viminalis were selected as experimental materials, and a 16-day hydroponic experiment with 0 and 1.0 mg·L-1 phenanthrene concentrations were conducted to study the dynamic changes of reactive oxygen, antioxidant enzymes, antioxidants and malondialdehyde (MDA) contents. Result The Results showed that: (1) Under phenanthrene treatment, the superoxide anion radical (O2·-) production and H2O2 content increased rapidly, then MDA content rose. Catalase (CAT) activity significantly increased on the 4th day, and the superoxide dismutase (SOD) and peroxidase (POD) activity increased on the 8th day. On the 16th day, no significant difference was found in H2O2 content between the samples treated with phenanthrene and that of the control. Meanwhile, the increment of O2·- and MDA also slowed down. (2) The contents of reduced glutathione (GSH) and glutathione reductase rose rapidly on the 4th day under phenanthrene treatment, and the activity of glutathione-s-transferase (GST) increased slowly. (3) Under phenanthrene treatment, the content of ascorbic acid was initially lower than the control group, but higher on the 16th day as the treatment time continued. Conclusion Under phenanthrene stress, O2·- is the main reactive oxygen causing cell membrane lipid peroxidation. SOD activity is always higher than that of the control group, but not enough to eliminate the increased O2·-. The increase of CAT and POD could eliminate the excessive H2O2. GSH is an effective antioxidant to resist the stress of phenanthrene and participates in the detoxification of phenanthrene through the catalysis of GST. -
Key words:
- Salix viminalis
- / phenanthrene
- / reactive oxygen
- / antioxidants
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