干旱胁迫下黄土高原4种乡土禾草抗氧化特性

采用盆栽实验,对干旱胁迫下黄土高原4种乡土禾草冰草、长芒草、无芒隐子草和白羊草叶片过氧化氢(H₂O₂)、丙二醛(MDA)含量、抗氧化酶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、脱氢抗坏血酸还原酶(DHAR)、单脱氢抗坏血酸还原酶(MDHAR)、谷胱甘肽过氧化物酶(GPX)活性和非酶抗氧化物质还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)、类胡萝卜素(Car)含量进行了测定。 结果表明:随着干旱胁迫程度的加剧,4种乡土禾草叶片H₂O₂、MDA含量均呈增加趋势,这说明它们均遭受了干旱所造成的氧化胁迫,且干旱程度越大其遭受的氧化胁迫也越大。由于4种乡土禾草均为禾本科植物并生存于相同的生态环境中,它们在抗氧化特性上具有一定共性。在60%FC和45%FC干旱胁迫下,4种乡土禾草均可以通过增加抗氧化酶SOD、CAT、APX、GR、DHAR、MDHAR、GPX活性和非酶抗氧化物质AsA含量来抵御干旱所造成的氧化胁迫。由于种属差异,4种乡土禾草的抗氧化特性也存在差异。在60%FC和45%FC干旱胁迫下,冰草、无芒隐子草和白羊草还通过增加非酶抗氧化物质Car含量增强抗氧化能力,长芒草和白羊草则还可通过增加POD活性抵御干旱。在60%FC干旱胁迫下,冰草还可通过增加非酶抗氧化物质GSH含量提高其抗氧化性。采用隶属函数法对4种乡土草种抗氧化能力的综合评价表明,冰草的抗氧化能力最强,其次为无芒隐子草和白羊草,长芒草的抗氧化能力最差。     

褪黑素对高温胁迫下黄瓜幼苗抗坏血酸代谢系统的影响

以‘津春4号’黄瓜幼苗为试材,采用叶面喷施的方法,研究了外源褪黑素对高温胁迫下黄瓜幼苗叶片抗坏血酸代谢系统的影响.结果表明:高温胁迫后,黄瓜幼苗叶片过氧化氢(H2O2)和丙二醛(MDA)含量明显增加;还原型抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量持续下降,脱氢抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量逐渐升高,AsA/DHA和GSH/GSSG大幅下降;抗坏血酸过氧化物酶(APx)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性明显升高,并在12 h达到最大.外施褪黑素能有效抑制高温胁迫下黄瓜幼苗叶片H2O2和MDA的积累,提高抗氧化物质AsA和GSH含量及抗坏血酸代谢相关酶APx、MDHAR、DHAR和GR活性,从而增强对H2O2的清除能力,抑制活性氧的产生,维持细胞膜的稳定性,减轻高温对植株造成的伤害,提高黄瓜幼苗抵御高温胁迫的能力.     

不同抗性苹果砧木叶片抗坏血酸代谢对干旱胁迫的响应

以抗旱性强的苹果砧木新疆野苹果[Malus sieversii (Ledeb.) Roem.]和抗旱性弱的平邑甜茶[M.hupehensis (Panlp.) Reld.]叶片为试材,在20%PEG-6000模拟干旱胁迫条件下,研究了抗坏血酸(AsA)含量、氧化还原状态、合成和代谢相关酶活性对干旱胁迫的响应。结果显示,在正常水分条件下,新疆野苹果和平邑甜茶叶片间AsA含量及代谢相关酶活性差异不显著。干旱胁迫过程中,二者之间叶片AsA、谷胱甘肽(GSH)、总谷胱甘肽和总抗坏血酸含量变化趋势基本一致,但新疆野苹果叶片中的含量增加幅度明显大于平邑甜茶;且与平邑甜茶相比,新疆野苹果叶片具有较高的L-半乳糖酸-1,4-内酯脱氢酶(GalLDH)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性及AsA/DHA(脱氢抗坏酸)和GSH/GSSG(氧化型谷胱甘肽)比率。研究表明,干旱胁迫下,新疆野苹果能够维持较高的AsA合成和再生能力,并具有维持高AsA水平特性,这可能与其具有较强的抗旱性相关。     

H_2S对干旱胁迫下白三叶幼苗抗氧化防御能力的影响

以‘拉丁诺’白三叶(Trifolium repens cv.‘Ladino’)为试验材料,研究外源H2S处理对PEG6 000(聚乙二醇)模拟干旱胁迫下白三叶叶片相对含水量(RWC)、膜脂过氧化、活性氧成分、抗氧化酶、抗坏血酸-谷胱甘肽循环代谢和非酶抗氧化物质的影响,以揭示H_2S调控白三叶抗旱性的生理机制。结果显示:(1)0.2 mmol/L的外源NaHS(H_2S供体)能显著提高干旱胁迫下白三叶的叶片相对含水量,维持显著较低的电解质渗透率(EL)和丙二醛(MDA)含量。(2)与直接干旱胁迫相比,干旱胁迫下外源添加NaHS处理的白三叶叶片内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性显著增强,抗坏血酸-谷胱甘肽循环代谢中关键酶抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)、单脱水抗坏血酸还原酶(MDHAR)和谷胱甘肽还原酶(GR)活性及其抗氧化中间产物抗坏血酸(AsA)、谷胱甘肽(GSH)含量也显著提高。(3)叶片类黄酮、总酚和原花青素的含量在一定的胁迫时间范围内亦显著增加,并伴随着活性氧成分O_2~(-·)产生速率和H_2O_2水平降低。研究认为,外源H2S能通过促进干旱胁迫下白三叶体内的多重抗氧化防御能力来提高其幼苗的抗旱性。     

外源表油菜素内酯对NaHCO3胁迫下黄瓜幼苗生长及氧化还原平衡的影响

以‘津研四号’黄瓜为试材,以30 mmol·L^-1NaHCO_3模拟盐碱环境,采用水培法研究了0.2μmol·L^-1外源2,4表油菜素内酯(2,4-epibrassinolide,EBR)对盐碱胁迫下黄瓜幼苗生长和活性氧代谢的影响.结果表明:NaHCO_3胁迫显著诱导了叶片及根系中O2-·的产生和H_2O_2的积累,导致丙二醛含量和电解质渗透率提高.NaHCO_3胁迫下,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、谷胱甘肽还原酶活性及还原型抗坏血酸、还原型谷胱甘肽含量随胁迫时间延长呈现先升后降的趋势.外源EBR显著提高了NaHCO_3胁迫下黄瓜叶片和根系中抗氧化酶活性、抗氧化物质的含量以及As A/DHA(双脱氢抗坏血酸)和GSH/GSSG(氧化型谷胱甘肽)比值,维持了植株内的氧化还原平衡,降低了活性氧积累水平,缓解了膜脂过氧化,从而提高了黄瓜幼苗的盐碱耐受性.     

外源表油菜素内酯对NaHCO3胁迫下黄瓜幼苗生长及氧化还原平衡的影响

以‘津研四号’黄瓜为试材,以30 mmol·L^-1 NaHCO₃模拟盐碱环境,采用水培法研究了0.2 μmol·L^-1外源2,4表油菜素内酯(2,4-epibrassinolide,EBR)对盐碱胁迫下黄瓜幼苗生长和活性氧代谢的影响.结果表明: NaHCO₃胁迫显著诱导了叶片及根系中O₂^-·的产生和H₂O₂的积累,导致丙二醛含量和电解质渗透率提高.NaHCO₃胁迫下,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、谷胱甘肽还原酶活性及还原型抗坏血酸、还原型谷胱甘肽含量随胁迫时间延长呈现先升后降的趋势.外源EBR显著提高了NaHCO₃胁迫下黄瓜叶片和根系中抗氧化酶活性、抗氧化物质的含量以及AsA/DHA(双脱氢抗坏血酸)和GSH/GSSG(氧化型谷胱甘肽)比值,维持了植株内的氧化还原平衡,降低了活性氧积累水平,缓解了膜脂过氧化,从而提高了黄瓜幼苗的盐碱耐受性.     

外源NO对铜胁迫下番茄幼苗根系抗坏血酸-谷胱甘肽循环的影响

采用营养液培养方法,研究外源NO对铜胁迫下番茄(Lycopersicon esculentum Mill.)幼苗根系抗坏血酸(AsA)-谷胱甘肽(GSH)循环中抗氧化物质和抗氧化酶系的影响.结果表明:外施适量NO(硝普钠)可提高铜胁迫下番茄幼苗根系AsA、GSH含量和AsA/DHA(氧化型抗坏血酸)、GSH/GSSG(氧化型谷胱甘肽),降低DHA和GSSG含量.添加100 μmol·L-1 BSO(谷胱甘肽合成酶抑制剂)处理下,外源NO可提高铜胁迫下番茄幼苗根系的AsA含量、AsA/DHA及抗坏血酸酶(AAO)、单脱氢抗坏血酸还原酶(MDHAR)和脱氢抗坏血酸还原酶(DHAR)比活性,降低DHA、GSH、GSSG含量及抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)比活性;添加250 μmol·L-1 BSO处理下,外源NO提高了铜胁迫下番茄幼苗根系的AsA、GSH、GSSG含量、AsA/DHA及APX和GR比活性,降低了DHA含量及AAO、DHAR和MDHAR比活性.说明外源NO影响了铜胁迫下番茄根系的AsA-GSH代谢循环,并通过调节AsA/DHA、GSH/GSSG的变化来减轻氧化胁迫,从而缓解铜胁迫对番茄根系的伤害.     

硫化氢对盐碱胁迫下裸燕麦叶片抗坏血酸-谷胱甘肽循环的调控效应

盐碱胁迫是植物遭受的常见非生物胁迫之一,气体信号硫化氢(H₂S)在植物响应盐碱胁迫中发挥着重要作用。为探讨H₂S对盐碱胁迫下裸燕麦抗坏血酸(AsA)-谷胱甘肽(GSH)循环的调控效应,以品种‘定莜9号’为材料,研究了喷施H₂S供体硫氢化钠(NaHS)或H₂S合成抑制剂羟胺(HA)对盐碱混合胁迫下植株生长、叶片活性氧、膜脂过氧化和AsA-GSH循环中抗氧化物质和关键酶的影响。结果表明: 喷施50 μmol·L^-1 NaHS可缓解50 mmol·L^-1盐碱混合胁迫对裸燕麦生长的抑制,降低超氧阴离子、H₂O₂、丙二醛、氧化型抗坏血酸(DHA)、还原型谷胱甘肽(GSH)和氧化型谷胱甘肽(GSSG)含量,提高AsA/DHA和GSH/GSSG,而对还原型抗坏血酸(AsA)含量无显著影响。喷施NaHS还提高了盐碱混合胁迫下裸燕麦叶片AsA合成关键酶L-半乳糖脱氢酶(GalDH)和L-半乳糖-1,4-内酯脱氢酶(GalLDH)及AsA-GSH循环中单脱氢抗坏血酸还原酶(MDHAR)活性,降低了抗坏血酸过氧化物酶(APX)和脱氢抗坏血酸还原酶(DHAR)活性,而对抗坏血酸氧化酶(AO)和谷胱甘肽还原酶(GR)活性的影响不大。增添HA后部分或完全解除了喷施NaHS的上述作用。这说明H₂S可通过促进AsA合成和增强MDHAR活性提高AsA-GSH循环效率,降低盐碱胁迫对裸燕麦的氧化伤害。     

外源一氧化氮供体对NaCl胁迫下多裂骆驼蓬幼苗叶片ASA-GSH循环的影响

研究了外源一氧化氮(NO)供体硝普钠(SNP)对NaCl胁迫下多裂骆驼蓬幼苗抗坏血酸(ASA)-谷胱甘肽(GSH)循环抗氧化系统及H2O2和丙二醛(MDA)含量的影响。结果表明,0.15mmol.L-1SNP能提高300mmol.L-1NaCl胁迫下多裂骆驼蓬幼苗叶片抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)和谷胱甘肽转硫酶(GST)活性,增加还原型抗坏血酸(ASA)和谷胱甘肽(GSH)含量,降低脱氢抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量,提高ASA/DHA、GSH/GSSG比率,降低H2O2和MDA水平,对单脱氢抗坏血酸还原酶(MDAR)和脱氢抗坏血酸还原酶(DHAR)活性无显著影响。NO信号转导途径关键酶鸟苷酸环化酶(GC)抑制剂亚甲基蓝(MB)逆转了SNP对盐胁迫下APX、GR、GST活性和ASA、GSH、DHA,H2O2、MDA含量及ASA/DHA、GSH/GSSG比率的调节效应。由此表明,NO可能通过GC介导的cGMP信号转导参与ASA-GSH循环活性氧清除系统的调节,从而缓解盐胁迫诱导的氧化伤害。     

外源NO对铜胁迫下番茄幼苗根系抗坏血酸谷胱甘肽循环的影响

采用营养液培养方法,研究外源NO对铜胁迫下番茄(Lycopersicon esculentum Mill.)幼苗根系抗坏血酸(AsA)-谷胱甘肽(GSH)循环中抗氧化物质和抗氧化酶系的影响.结果表明：外施适量NO(硝普钠)可提高铜胁迫下番茄幼苗根系AsA、GSH含量和AsA/DHA(氧化型抗坏血酸)、GSH/GSSG(氧化型谷胱甘肽),降低DHA和GSSG含量.添加100 μmol·L^-1 BSO(谷胱甘肽合成酶抑制剂)处理下,外源NO可提高铜胁迫下番茄幼苗根系的AsA含量、AsA/DHA及抗坏血酸酶(AAO)、单脱氢抗坏血酸还原酶(MDHAR)和脱氢抗坏血酸还原酶(DHAR)比活性,降低DHA、GSH、GSSG含量及抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)比活性;添加250 μmol·L^-1 BSO处理下,外源NO提高了铜胁迫下番茄幼苗根系的AsA、GSH、GSSG含量、AsA/DHA及APX和GR比活性,降低了DHA含量及AAO、DHAR和MDHAR比活性.说明外源NO影响了铜胁迫下番茄根系的AsA-GSH代谢循环,并通过调节AsA/DHA、GSH/GSSG的变化来减轻氧化胁迫,从而缓解铜胁迫对番茄根系的伤害.     

Nitric oxide is involved in the regulation of ascorbate and glutathione metabolism in Agropyron cristatum leaves under water stress

This study investigated the regulation of ascorbate and glutathione metabolism by nitric oxide in Agropyron cristatum leaves under water stress. The activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), L-galactono-1,4-lactone dehydrogenase (GalLDH) and γ-glutamylcysteine synthetase (γ-ECS), and the contents of NO, reduced ascorbic acid (AsA), reduced glutathione (GSH), total ascorbate and total glutathione increased under water stress. These increases were suppressed by pretreatments with NO synthesis inhibitors N ^G-nitro-L-arginine methyl ester (L-NAME) and 4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). However, application of L-NAME and cPTIO to plants sufficiently supplied with water did not affect the activities of above mentioned enzymes and the contents of NO and above mentioned antioxidants. Pretreatments with L-NAME and cPTIO increased the malondialdehyde (MDA) content and electrolyte leakage of plants under water stress. Our results suggested that water stress-induced NO is a signal that leads to the upregulation of ascorbate and glutathione metabolism and has important role for acquisition of water stress tolerance.     

Effects of exogenous hydrogen sulfide on the redox states of ascorbate and glutathione in maize leaves under salt stress

This study investigated the effects of exogenous hydrogen sulfide (H₂S) on the redox states of ascorbate (AsA) and glutathione (GSH) in maize leaves under NaCl (100 mM) stress. Salt stress increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), Γ-glutamylcysteine synthetase (Γ-ECS), and L-galactono-1,4-lactone dehydrogenase (GalLDH), malondialdehyde content and electrolyte leakage, and reduced the ratios of reduced and oxidised forms of AsA (AsA/DHA) and GSH (GSH/GSSG) compared with control. Pretreatment with NaHS (H₂S donor) further enhanced the activities of the above enzymes except MDHAR and ameliorated the decrease in the ratios of AsA/DHA and GSH/GSSG compared with the salt stress alone. Pretreatment with NaHS significantly reduced the malondialdehyde content and electrolyte leakage induced by the salt stress. Pretreatment with NaHS alone did not affect any of the above mentioned parameters compared with the control. Our results suggest that exogenous H2S could maintain the redox states of ascorbate and glutathione by up-regulating the ascorbate and glutathione metabolism and thus play an important role for acquisition of salt stress tolerance in maize.     

Regulation of the ascorbate-glutathione cycle in wild almond during drought stress

In wild species of almond (Prunus spp.), the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), as well as the levels of ascorbate/glutathione pools and H₂O₂ were subjected to water deficit and shade conditions. After 60 days of water shortage, the species were subjected to a rewatering treatment. During water recovery, leaves exposed to sunlight and leaves under shade conditions of about 20–35% of environmental irradiance were sampled. After 70 days without irrigation, mean predawn leaf water potential of all the species fell from −0.32 to −2.30 MPa and marked decreases in CO₂ uptake and transpiration occurred. The activities of APX, MDHAR, DHAR, and GR increased in relation to the severity of drought stress in all the wild species studied. Generally, APX, MDHAR, DHAR, and GR were down-regulated during the rewatering phase and their activities decreased faster in shaded leaves than in sun-exposed leaves. The levels in total ascorbate, glutathione, and H₂O₂ were directly related to the increase in drought stress and subsequently decreased during rewatering. The antioxidant response of wild almond species to drought stress limits cellular damage caused by reactive oxygen species during periods of water deficit and may be of key importance for the selection of drought-resistant rootstocks for cultivated almond.     

Effects of lanthanum on the ascorbate and glutathione metabolism of Vigna radiata seedlings under salt stress

In order to elucidate the role of lanthanum (La) in response of Vigna radiata to a salt stress, we investigated the effects of La on the ascorbate and glutathione metabolism. The results show that in comparison with a control, the salt stress increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), γ-glutamylcysteine synthetase (γ-ECS), and L-galactono-1,4-lactone dehydrogenase (GalLDH), and the content of ascorbic acid (AsA) and glutathione (GSH). It also increased the malondialdehyde content (MDA) and electrolyte leakage. The salt stress significantly decreased the ratios of AsA/dehydroascorbate (DHA) and GSH/glutathione disulphide (GSSG) compared with the control. The pretreatment with La not only significantly increased the activities of the above enzymes, the content of AsA, GSH, and the ratios of AsA/DHA and GSH/GSSG, but also significantly reduced the MDA content and electrolyte leakage compared with the salt stress alone. Our results suggest that La could up-regulate the ascorbate and glutathione metabolisms and could have an important role for acquisition of salt stress tolerance in Vigna radiata.     

Role of the Ascorbate-Glutathione Cycle of Mitochondria and Peroxisomes in the Senescence of Pea Leaves

We investigated the relationship between H₂O₂ metabolism and the senescence process using soluble fractions, mitochondria, and peroxisomes from senescent pea (Pisum sativum L.) leaves. After 11 d of senescence the activities of Mn-superoxide dismutase, dehydroascorbate reductase (DHAR), and glutathione reductase (GR) present in the matrix, and ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) activities localized in the mitochondrial membrane, were all substantially decreased in mitochondria. The mitochondrial ascorbate and dehydroascorbate pools were reduced, whereas the oxidized glutathione levels were maintained. In senescent leaves the H₂O₂ content in isolated mitochondria and the NADH- and succinate-dependent production of superoxide (O₂^·−) radicals by submitochondrial particles increased significantly. However, in peroxisomes from senescent leaves both membrane-bound APX and MDHAR activities were reduced. In the matrix the DHAR activity was enhanced and the GR activity remained unchanged. As a result of senescence, the reduced and the oxidized glutathione pools were considerably increased in peroxisomes. A large increase in the glutathione pool and DHAR activity were also found in soluble fractions of senescent pea leaves, together with a decrease in GR, APX, and MDHAR activities. The differential response to senescence of the mitochondrial and peroxisomal ascorbate-glutathione cycle suggests that mitochondria could be affected by oxidative damage earlier than peroxisomes, which may participate in the cellular oxidative mechanism of leaf senescence longer than mitochondria.     

Effect of Selenium on Ascorbate�CGlutathione Metabolism During PEG-induced Water Deficit in Trifolium repens L.

To elucidate the effect of selenium (Se) on the ascorbate?Cglutathione (ASC?CGSH) cycle under drought stress, the activities of antioxidant enzymes and the levels of molecules involved in ASC?CGSH metabolism were studied in Trifolium repens seedlings subjected to polyethylene glycol (PEG)-induced water deficit alone or combined with 5???M Na₂SeO₄. Compared to the control, H₂O₂, thiobarbituric acid reactive substances (TBARS), ascorbate (ASC), dehydroascorbate (DHA), and glutathione disulfide (GSSG) contents increased, whereas a constant content of glutathione (GSH) and decreases in ASC/DHA and GSH/GSSG ratios were observed in the presence of PEG. The activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were upregulated, except for monodehydroascorbate reductase (MDHAR) activity during PEG-induced water deficit. Se application decreased the contents of H₂O₂, TBARS, DHA, and GSSG, increased the levels of GSH and ASC, and inhibited the decreases of ASC/DHA and GSH/GSSG ratios. Although it did not affect APX activity significantly, Se addition improved the activities of MDHAR, DHAR, and GR. Furthermore, GR activity showed the highest increase followed by that of DHAR and MDHAR in decreasing order. These data indicated that fluctuations in ASC?CGSH metabolism resulting from Se may have a positive effect on drought stress mitigation, and the regulation in the ASC?CGSH cycle can be attributed mainly to GR and DHAR in PEG?+?Se-treated T. repens seedlings.     

Ascorbate-glutathione metabolism during PEG-induced water deficit in <Emphasis Type="Italic">Trifolium repens</Emphasis>

In order to elucidate the response of the ascorbate-glutathione (ASC-GSH) cycle to drought stress, the activities of antioxidant enzymes and the levels of molecules involved in the ASC-GSH metabolism were studied in Trifolium repens L. seedlings subjected to PEG-induced water deficit. Compared to the control, the contents of H₂O₂, thiobarbituric acid reactive substances (TBARS), ascorbate (ASC), dehydroascorbate (DHA), and glutathione disulfide (GSSG) increased in PEG-treated seedlings, whereas the glutathione (GSH) content kept constant during the drought period. Further more, the ASC/DHA and GSH/GSSG ratios decreased in the presence of PEG. Except for that of monodehydroascorbate reductase (MDHAR), the activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were up-regulated during water deficit, and the increases in APX and DHAR activities were much higher than those in GR activity. These data indicate that fluctuations in the ASC-GSH metabolism resulted from PEG treatment may have a positive effect on drought stress mitigation in T. repens.     

Selenium Pretreatment Upregulates the Antioxidant Defense and Methylglyoxal Detoxification System and Confers Enhanced Tolerance to Drought Stress in Rapeseed Seedlings

In order to observe the possible regulatory role of selenium (Se) in relation to the changes in ascorbate (AsA) glutathione (GSH) levels and to the activities of antioxidant and glyoxalase pathway enzymes, rapeseed (Brassica napus) seedlings were grown in Petri dishes. A set of 10-day-old seedlings was pretreated with 25 μM Se (Sodium selenate) for 48 h. Two levels of drought stress (10% and 20% PEG) were imposed separately as well as on Se-pretreated seedlings, which were grown for another 48 h. Drought stress, at any level, caused a significant increase in GSH and glutathione disulfide (GSSG) content; however, the AsA content increased only under mild stress. The activity of ascorbate peroxidase (APX) was not affected by drought stress. The monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) activity increased only under mild stress (10% PEG). The activity of dehydroascorbate reductase (DHAR), glutathione S-transferase (GST), glutathione peroxidase (GPX), and glyoxalase I (Gly I) activity significantly increased under any level of drought stress, while catalase (CAT) and glyoxalase II (Gly II) activity decreased. A sharp increase in hydrogen peroxide (H₂O₂) and lipid peroxidation (MDA content) was induced by drought stress. On the other hand, Se-pretreated seedlings exposed to drought stress showed a rise in AsA and GSH content, maintained a high GSH/GSSG ratio, and evidenced increased activities of APX, DHAR, MDHAR, GR, GST, GPX, CAT, Gly I, and Gly II as compared with the drought-stressed plants without Se. These seedlings showed a concomitant decrease in GSSG content, H₂O₂, and the level of lipid peroxidation. The results indicate that the exogenous application of Se increased the tolerance of the plants to drought-induced oxidative damage by enhancing their antioxidant defense and methylglyoxal detoxification systems.     

乙烯与NO互作对镉胁迫下荷花的抗坏血酸-谷胱甘肽循环的影响

以荷花‘微山湖红莲’实生苗为试验材料,研究镉(Cd,50 μmol·L^-1)胁迫下,外源乙烯前体1-氨基环丙烷羧酸(ACC,100 μmol·L^-1)、ACC与一氧化氮合酶(NOS)抑制剂N-硝基-L-精氨酸(L-NNA,200 μmol·L^-1)、ACC与硝酸还原酶(NR)抑制剂钨酸钠(Tu,1 mmol·L^-1),ACC与一氧化氮(NO)清除剂2-苯基-4,4,5,5-四甲基咪唑啉-3-氧代-1-氧(PTIO,200 μmol·L^-1),外源NO供体硝普钠(SNP,500 μmol·L^-1)、SNP与乙烯信号转导抑制剂硫代硫酸银(STS,100 μmol·L^-1)处理下荷花幼苗叶片的受害程度及抗坏血酸(AsA)-谷胱甘肽(GSH)循环的变化情况.结果表明: Cd胁迫下,荷花叶片受害症状明显,其相对电导率、丙二醛(MDA)、AsA和GSH含量显著上升,抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、单脱氢抗坏血酸还原酶(MDHAR)和脱氢抗坏血酸还原酶(DHAR)活性明显降低;ACC的添加进一步增加了Cd对荷花叶片的毒害症状,并加剧了4种抗氧化酶活性的降低,但增加了抗氧化剂的含量;SNP的添加对荷花叶片的伤害起到加重作用,并导致GR和MDHAR活性降低以及AsA和GSH含量的升高;PTIO可显著提高Cd和ACC复合处理下荷花叶片APX、GR、MDHAR和DHAR的活性并降低AsA和GSH的含量,而L-NNA和Tu效果不如PTIO明显;STS可显著缓解Cd和SNP复合处理下荷花叶片的毒害症状,并提高4种抗氧化酶的活性、降低AsA和GSH的含量.由此说明,乙烯和NO在AsA-GSH循环中存在互作,二者相互促进,共同调控AsA-GSH循环,进而参与调控荷花对Cd胁迫的响应.