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.     

一氧化氮参与外源谷胱甘肽对盐胁迫下番茄幼苗抗氧化损伤的调控

采用营养液水培,研究外源谷胱甘肽(GSH)对NaCl和NaCl+Hb(牛血红蛋白,一种一氧化氮清除剂)处理下番茄(Lycopersicon esculentum)幼苗叶片中一氧化氮合酶(NOS)活性及其一氧化氮(NO)水平、膜脂过氧化程度、活性氧(ROS)积累和ROS清除能力的影响。结果表明:施用Hb使盐胁迫下番茄幼苗叶片的氧化损伤程度加剧,NO含量下调,但对GSH含量无显著影响。外源GSH的施用显著提高了盐胁迫下番茄幼苗叶中内源GSH与NO水平,单脱氢抗坏血酸还原酶(MDHAR)和硝酸还原酶(NR)活性,超氧化物歧化酶(SOD)活性(除72 h),过氧化氢酶(CAT)活性(除48 h),处理48和72 h的谷胱甘肽还原酶(GR)、抗坏血酸过氧化物酶(APX)和脱氢抗坏血酸还原酶(DHAR)活性;降低电解质渗透率、硫代巴比妥酸(TBARS)含量以及处理48和72 h的过氧化氢(H_2O_2)和超氧阴离子(O_2ˉ·)含量。外源喷施GSH亦显著提高NaCl+Hb处理下番茄叶中抗坏血酸(AsA)、GSH和NO水平,CAT和APX活性,处理24和48 h的NR活性以及处理48和72 h的NOS活性;降低电解质渗透率及H_2O_2和TBARS含量。表明外源GSH通过介导内源GSH和NO水平上调,提高抗氧化酶活性和ROS的清除能力来缓解NaCl和NaCl+Hb处理导致的氧化损伤。因此,NO参与了外源GSH对盐胁迫下番茄幼苗抗氧化损伤的调控。     

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.     

24-表油菜素内酯预处理对干旱胁迫下葡萄幼苗抗氧化系统和渗透调节物质的影响

以酿酒葡萄‘雷司令’(Riesling)一年生营养袋扦插苗为材料,采用人工气候室水培试验,考察在聚乙二醇6000(PEG)模拟干旱条件下,不同浓度(0.05、0.10和0.20mg/L)24-表油菜素内酯(EBR)预处理对‘雷司令’幼苗活性氧、抗氧化物质、渗透调节物质含量和抗氧化酶活性的影响,以揭示EBR预处理对干旱胁迫下葡萄幼苗的抗旱机理。结果显示:(1)与正常生长(对照)相比,干旱胁迫显著提高葡萄幼苗叶片中超氧阴离子自由基(■)、过氧化氢(H_2O_2)和丙二醛(MDA)含量;与干旱胁迫处理(PEG)相比,不同浓度EBR预处理均可降低叶片中■、H_2O_2和MDA的含量。(2)与对照相比,PEG处理显著降低葡萄幼苗叶片的抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量;与PEG处理相比,各浓度EBR预处理均可显著提高葡萄叶片AsA与GSH的含量,且以0.10mg/LEBR处理效果最好。(3)随着干旱胁迫时间的延长,葡萄幼苗叶片中的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)与抗坏血酸过氧化物酶(APX)活性均呈先上升后下降的变化趋势,而在正常生长条件下酶活性基本保持不变;EBR预处理的葡萄叶片SOD、CAT、POD和APX活性均始终高于同期PEG处理。(4)PEG处理条件下,渗透调节物质脯氨酸和可溶性蛋白的含量整体高于对照;与PEG处理相比,不同浓度EBR预处理在干旱胁迫中后期均能显著提高葡萄叶片中脯氨酸和可溶性蛋白含量。研究表明,在干旱胁迫下,外源EBR预处理能够提高葡萄叶片抗氧化系统酶活性和渗透调节物质含量,有效降低干旱胁迫诱导的活性氧过度积累及膜脂过氧化程度,提高葡萄幼苗的抗旱能力,且以0.10mg/L EBR处理效果最佳。     

外源褪黑素对干旱胁迫下牡丹幼苗生理特性的影响

为探究褪黑素(Melatonine,MT)对牡丹幼苗抗旱性的影响及生理机制,以牡丹品种凤丹(Paeonia ostii Fengdan)幼苗为试材,研究不同浓度外源褪黑素(50、100和200 μmol/L)对干旱胁迫下牡丹幼苗生长及生理特性的影响。结果表明,干旱胁迫严重限制了牡丹幼苗的生长和光合作用,叶片细胞脂质过氧化及伤害指数增加,引起氧化应激及渗透调节反应。经外源褪黑素预处理能够减轻干旱胁迫对牡丹幼苗的伤害,具体表现为根系、茎叶及总干物质量提高;减少叶绿素a、叶绿素b及类胡萝卜素等光合色素降解,改善光合作用及PSⅡ电子传输能力;降低丙二醛(MDA)、过氧化氢(H_2O_2)、超氧阴离子(O_2~-)含量及细胞膜质伤害指数(MII),提高超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)及谷胱甘肽还原酶(GR)等抗氧化酶活性减少脂质过氧化;促进渗透调节物质积累。总之,以100 μmol/L MT处理对牡丹幼苗抗旱性提高效果最好。外源褪黑素预处理能提高干旱胁迫下牡丹幼苗光合荧光特性、抗氧化和渗透调节能力,促进干旱胁迫下牡丹幼苗生长。     

外源硝酸钙对盐胁迫下黄瓜幼苗叶片抗氧化系统及膜质子泵活性的影响

采用营养液水培法,以较耐盐黄瓜品种"新泰密刺"为试验材料,研究了叶面喷施硝酸钙对盐胁迫(NaCl65mmol·L-1)下黄瓜幼苗活性氧、谷胱甘肽-抗坏血酸循环(GluAsA)中抗氧化酶和抗氧化物质及膜质子泵活性的影响。结果表明:叶面喷施硝酸钙能够显著降低盐胁迫下黄瓜幼苗叶片超氧阴离子(O.2-)产生速率和丙二醛(MDA)含量;显著提高盐胁迫下黄瓜幼苗叶片抗坏血酸过氧化物酶(APX)和脱氢抗坏血酸还原酶(DHAR)等酶活性、抗氧化物质抗坏血酸(AsA)含量、AsA/DHA和GSH/GSSG比值及质膜和液泡膜H+-ATPase和H+-PPase活性。表明外源硝酸钙通过提高Glu-AsA抗氧化系统和膜质子泵活性,降低活性氧对叶片的伤害,增强了植株抗氧化能力和对离子的区域化,进而提高植株盐胁迫耐性。     

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α-萘乙酸对花期长期干旱大豆叶片抗氧化系统的影响

以不同耐旱型品种‘南农99-6’和‘科丰1号’大豆为材料,2012年在南京农业大学牌楼试验站进行为期110 d的盆栽试验,研究大豆花期叶面喷施α-萘乙酸(NAA)对长期干旱条件下大豆植株抗氧化系统的影响.结果表明:干旱胁迫显著降低了大豆地上部干物质量,叶片中丙二醛(MDA)含量及活性氧(ROS)水平显著升高,同时,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)、单脱氢抗坏血酸还原酶(MDHAR)、谷胱甘肽还原酶(GR)和谷胱甘肽过氧化物酶(GPX)活性,还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)含量及AsA/DHA(双脱氢抗坏血酸)和GSH/GSSG(氧化型谷胱甘肽)比值显著升高,其中‘科丰1号’大豆的抗氧化能力更高,从而维持较低的ROS水平和MDA含量.NAA可显著提高叶片中的APX、POD、CAT、MDHAR活性及AsA/DHA、GSH/GSSG比值,其中‘科丰1号’大豆叶片的脱氢抗坏血栓还原酶(DHAR)活性和AsA含量极显著增加.     

盐及干旱胁迫对油菜抗氧化系统和RbohC、RbohF基因表达的影响

以白菜型油菜‘陇油6号’和‘天油2号’为试验材料,经MAPK抑制剂U0126、H_2O_2清除剂DMTU、NADPH氧化酶抑制剂DPI和IMD预处理后再分别进行盐胁迫、PEG-6000模拟干旱胁迫,研究其对两种油菜幼苗活性氧、抗氧化酶活性和RbohC、RbohF基因表达的影响.结果表明:盐胁迫和PEG-6000模拟干旱胁迫下,两种白菜型油菜中H_2O_2积累量上升,O_2^-·积累量下降,抗氧化酶(超氧化物歧化酶SOD、过氧化氢酶CAT、抗坏血酸过氧化物酶APX和谷胱甘肽还原酶GR)活性和RbohC、RbohF基因表达均升高.与单独胁迫处理相比,两种油菜O_2^-·积累、抗氧化酶活性和RbohC、RbohF基因的表达量均明显降低,经DMTU、DPI和IMD预处理后再分别进行盐和干旱胁迫,H_2O_2积累量下降,但U0126预处理后再进行胁迫处理,H_2O_2积累量上升.说明NADPH氧化酶、MAP激酶级联途径、H_2O_2参与了盐、干旱胁迫下活性氧产生、抗氧化酶活性变化和RbohC、RbohF基因表达的调控.     

外源SNP对盐胁迫下甜瓜幼苗生长及抗氧化酶活性的影响北大核心CSCD

为明确外源一氧化氮(NO)对甜瓜幼苗耐盐性的影响,该研究以甜瓜品种‘农大甜10号’为试验材料,在300 mmol·L^(-1)NaCl胁迫条件下,叶面喷施不同浓度(50、100、150、200、250μmol·L^(-1))外源NO供体硝普钠(SNP),分析甜瓜幼苗生长、光合色素含量、细胞膜透性、抗氧化酶活性、渗透调节物质含量的变化。结果表明:(1)盐胁迫显著抑制甜瓜幼苗的生长,同时显著降低叶片光合色素含量、细胞膜透性、抗氧化酶活性、渗透调节物质含量。(2)叶面喷施150μmol·L^(-1)SNP能够显著提高盐胁迫下甜瓜幼苗的株高、茎粗、干鲜重、壮苗指数,并显著提高盐胁迫下甜瓜幼苗的光合色素含量,从而提高甜瓜的光合作用。(3)喷施150μmol·L^(-1)SNP可显著提高盐胁迫下甜瓜幼苗超氧化物歧化酶(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)、单脱氢抗坏血酸还原酶(MDHAR)及脱氢抗坏血酸还原酶(DHAR)的活性,显著降低盐胁迫下甜瓜幼苗的丙二醛(MDA)、过氧化氢(H_(2)O_(2))含量及超氧阴离子(O^(-)·_(2))产生速率。(4)喷施150μmol·L^(-1)SNP可显著提高盐胁迫下甜瓜幼苗叶片脯氨酸(Pro)和可溶性蛋白的含量。研究认为,在盐胁迫环境下,适宜浓度的外源SNP(150μmol·L^(-1))可通过提高甜瓜幼苗的抗氧化酶活性以及光合色素和小分子可溶性有机化合物含量来增强活性氧的清除能力,降低膜脂过氧化作用,有效减轻盐胁迫对幼苗的伤害,从而增强其耐盐性,促进幼苗生长。     

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.     

Effect of pretreatment with hydrogen sulfide donor sodium hydrosulfide on heat tolerance in relation to antioxidant system in maize (Zea mays) seedlings

Hydrogen sulfide (H₂S) is a signal molecule that is involved in plant growth, development and the acquisition of stress tolerance including heat tolerance, but the mechanism of H₂S-induced heat tolerance is not completely clear. In present study, the effect of sodium hydrosulfide (NaHS), a H₂S donor, treatment on heat tolerance of maize seedlings in relation to antioxidant system was investigated. The results showed that NaHS treatment improved survival percentage of maize seedlings under heat stress in a concentration-dependent manner, indicating that H₂S treatment could improve heat tolerance of maize seedlings. To further study mechanism of NaHS-induced heat tolerance, catalase (CAT), guaiacol peroxidase (GPX), superoxide dismutase (SOD), glutathione reductase (GR) and ascorbate peroxidase (APX) activities, and glutathione (GSH) and ascorbic acid (AsA) contents in maize seedlings were determined. The results showed that NaHS treatment increased the activities of CAT, GPX, SOD and GR, and GSH and AsA contents as well as the ratio of reduced antioxidants to total antioxidants [AsA/(AsA+DHA) and GSH/(GSH +GSSG)] in maize seedlings under normal culture conditions compared with the control. Under heat stress, antioxidant enzymes activities, antioxidants contents and the ratio of the reduced antioxidants to total antioxidants in control and treated seedlings all decreased, but NaHS-treated seedlings maintained higher antioxidant enzymes activities and antioxidants levels as well as the ratio of reduced antioxidants to total antioxidants. All of above-mentioned results suggested that NaHS treatment could improve heat tolerance of maize seedlings, and the acquisition of this heat tolerance may be relation to enhanced antioxidant system activity.     

外源H_2S对NO_3~-胁迫下番茄幼苗生理生化特性的影响

采用营养液水培方法,通过外源施加H2S供体NaHS(100μmol/L),研究了信号分子H2S对100mmol/L NO3-胁迫下番茄幼苗生理生化特性的影响。结果表明:(1)NO3-胁迫下,随着处理时间的延长,番茄幼苗的株高、根长、鲜重和干重显著降低,叶绿素(a、b)含量、净光合速率、气孔导度、蒸腾速率均显著降低,而胞间CO2浓度以及丙二醛(MDA)、H2O2含量增加,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性显著降低,抗坏血酸(AsA)和还原性谷胱甘肽(GSH)含量显著降低。(2)与NO3-胁迫处理相比,外源NaHS处理1、3、5d后,番茄幼苗的株高、根长、鲜重和干重显著增加,叶绿素(a、b)含量、净光合速率、气孔导度、蒸腾速率均显著升高,而胞间CO2浓度显著降低;MDA和H2O2含量降低,SOD、POD、CAT和APX活性显著增强,AsA和GSH含量显著增加,而且幼苗的硝酸还原酶、谷氨酰胺合成酶、谷氨酸合酶的活性显著增强;L-半胱氨酸脱巯基酶活性和内源H2S含量增加。研究认为,外源H2S可能通过提高抗氧化物酶的活性和增加抗氧化物质含量来缓解NO3-对番茄幼苗造成的伤害,从而增强其对NO3-胁迫耐性。     

Spermidine application enhances tomato seedling tolerance to salinity-alkalinity stress by modifying chloroplast antioxidant systems

The purpose of this study was to elucidate whether exogenous spermidine (Spd) protection of tomato (Solanum lycopersicum L.) seedlings under salinity-alkalinity stress is associated with antioxidant enzymes in the chloroplast. The effects of exogenous Spd on antioxidant enzyme activity and antioxidant content in the chloroplast were evaluated in seedlings of salt-sensitive ecotype (Zhongza 9) grown in a 75 mM salinity-alkalinity solution, with or without 0.25 mM Spd foliar spraying. Results showed that salinity-alkalinity stress increased MDA content, superoxide anion O₂^?- generation rate, superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) activities and ratio of AsA/DHA and reduced contents of ascorbate (AsA), dehydroascorbate (DHA), AsA+DHA, glutathione (GSH), oxidized glutathione (GSSG), GSH+GSSG, dehydroascorbate reductase (DHAR) activity and ratio of GSH/GSSG in chloroplasts. The exogenous Spd application combined with salinity-alkalinity stress decreased the O₂^?- generation rate and MDA content compared to salinity-alkalinity stress alone. The exogenous Spd also increased AsA-GSH cycle components and increased all antioxidant enzyme activities in most cases. Therefore, exogenous Spd alleviates salinity-alkalinity stress damage using antioxidant enzymes and non-enzymatic systems in chloroplasts.     

Hydrogen sulfide protects soybean seedlings against drought-induced oxidative stress

Increasing evidence indicates that hydrogen sulfide (H₂S) is the third “gas signal molecule” after NO and CO in animal. In the present study, we found that soybean (Glycine max L.) seedlings sprayed with exogenous H₂S donor NaHS prolonged the longer survival time of life, and enlarged higher biomass of both leaf and root than in non-sprayed controls under continuous drought stress. With the continuous drought stress, the content of chlorophyll in the leaves of both Xu-1 and Xu-6 cultivar of soybean decreased dramatically. The drought-induced decrease in chlorophyll could be alleviated by spraying H₂S donor. It was also shown that spraying with H₂S donor dramatically retained higher activities of superoxide dismutase (SOD, EC 1.1.5.1.1), catalase (CAT, EC1.11.1.6) and lower activity of lipoxygenases (LOX, EC 1.13.11.12), delayed excessive accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion (O₂^·−) compared with the control. These results suggest that H₂S can increase drought tolerance in soybean seedlings by acting as an antioxidant signal molecule for the response.     

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.     

Responses of the antioxidant defense system to drought stress in the leaves of Fargesia denudata seedlings,the staple food of the giant panda

The responses of the antioxidant defense system in plant species to drought stress are still relatively unknown. In order to further understand how the system responds to drought stress, the leaves of Fargesia denudata seedlings were investigated. Antioxidant enzyme activities, antioxidant contents, hydrogen peroxide (H₂O₂), superoxide anion (O ₂ ^·? ) and MDA contents in the seedling leaves were measured under well-watered (WW), moderate drought-stressed (MD), and severe drought-stressed (SD) treatments. Although drought stress significantly increased H₂O₂ and O ₂ ^·? levels in F. denudata leaves, only weak lipid peroxidation was observed. This is attributed to the higher superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) activities in F. denudata leaves during the entire drought period. Reduced and oxidized ascorbate (AsA and DHA) contents were almost not affected by drought except that DHA under SD showed an obvious increase on day 30. Furthermore, reduced glutathione (GSH) content under drought stress significantly decreased, while oxidized glutathione (GSSG) markedly increased under SD on days 30 and 45 as well as under MD on day 30; as a result, the ratio GSH/GSSG declined considerably. These results indicated that GSH was involved in scavenging H₂O₂ and O ₂ ^·? under drought stress and it was more sensitive to drought stress in scavenging H₂O₂ and O ₂ ^·? than AsA. As a result, a highly efficient antioxidant defense system in drought-stressed F. denudate leaves operated mainly through the synergistic functioning of SOD, CAT, APX, MDHAR, DHAR, GR, and GSH against oxidative damage.     

高温胁迫下外源褪黑素对黄瓜幼苗活性氧代谢的影响

以黄瓜品种‘津春4号’为试材,用叶面喷施的方法,研究了高温胁迫条件下外源褪黑素(melatonin,MT)对黄瓜幼苗活性氧（ROS）代谢的影响.结果表明：外源MT能显著降低高温胁迫下黄瓜叶片超氧阴离子自由基（O₂^-.）产生速率、过氧化氢（H₂O₂）含量、电解质漏渗率（relative electric conductivity, REC）及丙二醛(MDA)含量,增强黄瓜幼苗叶片中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性,提高抗坏血酸（AsA）、谷胱甘肽（GSH）及可溶性蛋白质含量.说明MT预处理能抑制高温胁迫条件下黄瓜幼苗体内ROS的产生,提高抗氧化酶系的活性及抗氧化物质的含量,降低膜质过氧化水平,保护脂膜的完整性,减少电解质的外渗,减轻高温胁迫对幼苗造成的伤害,提高幼苗抗高温胁迫的能力.     

EFFECTS OF CALCIUM NITRATE STRESS ON ASCORBATE-GLUTATHIONE CYCLE METABOLISM IN LEAVES OF HYDROPONICALLY-GROWN GRAFTED EGGPLANT SEEDLINGS

 以日本引进的设施专用耐盐茄(Solanum melongena)品种‘Torvum Vigor’为砧木, 栽培茄(S. torvum)品种‘苏崎茄’为接穗, 用营养液栽培, 对80 mmol&;#8226;L^–1 Ca(NO₃)₂胁迫下茄子嫁接苗和自根苗叶片抗坏血酸-谷胱甘肽循环系统中抗氧化酶活性和抗氧化物及H₂O₂含量进行比较。结果表明, Ca(NO₃)₂胁迫下茄子幼苗叶片H₂O₂含量有所增加, 但嫁接苗叶片H₂O₂含量显著低于自根苗。Ca(NO₃)₂胁迫下嫁接苗叶片抗氧化酶(APX、DHAR和GR)活性、AsA和GSH再生率、氧化还原力(AsA/DHA值和GSH/GSSG值)均显著高于自根苗。综上所述, Ca(NO₃)₂胁迫下嫁接苗保持良好的AsA-GSH循环效率, 清除H₂O₂效率较高, 细胞受氧化损伤程度较轻, 表现出较强的耐盐性。