外源抗坏血酸对臭氧胁迫下水稻光合及生长参数的影响

为研究臭氧浓度变化对水稻生长的影响及外源抗坏血酸的防护作用,在田间原位条件下,利用开顶式气室(OTCs)研究了外源抗坏血酸对O3胁迫下水稻光合及生长参数的影响.结果表明:在O3胁迫下,叶片的光合色素含量、气体交换参数、净同化率、相对生长速率及粒/叶面积(cm2)均显著下降;喷施外源抗坏血酸后,叶绿素a含量、叶绿素a/叶绿素b以及水稻叶片的光合速率、蒸腾速率显著升高,而叶绿素b含量和气孔导度变化不显著;外源抗坏血酸对O3胁迫下水稻的净同化率、相对生长速率及粒/叶面积(cm2)影响比较显著,特别是粒/叶面积(cm2)的提高有利于水稻源、库协调发展,为提高水稻产量和改进品质奠定了物质基础.     

CO2激光与外源NO对低温胁迫小麦的防护效应

以冬小麦‘小堰22号’为试验材料,研究了CO2激光与外源一氧化氮(NO)复合作用对低温胁迫(4℃)下小麦幼苗自由基双氧水(H2O2)、超氧阴离子(O2?)浓度,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)、一氧化氮合成酶(NOS)活性,一氧化氮(NO)及蛋白质含量,及幼苗生长发育的影响。结果表明:与单独低温胁迫相比,外源NO处理后低温胁迫和CO2激光处理后低温胁迫都显著降低了H2O2和O2?浓度,提高了SOD、CAT、POD、APX、NOS活性,NO和蛋白质含量,促进幼苗生长发育。外源NO处理后再进行CO2激光辐射,虽然可以降低低温胁迫下幼苗H2O2和O2?浓度,提高SOD、CAT、POD、APX、NOS活性及NO和蛋白质浓度,促进幼苗生长发育,但其保护效应明显低于外源NO处理后低温胁迫和CO2激光处理后低温胁迫的效果。上述结果说明,NO对低温胁迫的防护效应优于NO和CO2激光复合处理。因此,建议在农业生产中单独采用NO处理或者CO2激光处理,可以促进农作物对低温胁迫的抗性。     

NO对低温胁迫下玉米种子萌发及幼苗生理特性的影响

以4℃模拟低温胁迫状况,研究了外源一氧化氮（NO）供体硝普钠（SNP）对低温胁迫下玉米种子萌发、幼苗生长和生理特性的影响。结果表明,低温胁迫下,玉米种子萌发和幼苗生长受到抑制,叶片丙二醛（MDA）含量和相对电导率显著上升,叶片相对含水量、脯氨酸含量和叶绿素含量显著降低。不同浓度的SNP均能显著提高低温胁迫下玉米种子的发芽率、发芽势、发芽指数和活力指数;促进低温胁迫下玉米幼苗的生长;抑制低温胁迫下玉米幼苗叶片MDA含量的上升,降低叶片质膜相对透性,增加相对含水量、脯氨酸含量和叶绿素含量。表明外源NO可缓解低温胁迫对玉米种子萌发及幼苗生长的抑制作用,缓解低温胁迫引起的膜脂过氧化,保护细胞膜免受或减少损伤,提高植物抗低温胁迫的能力。在SNP不同的使用浓度中,以100μmol·L-1SNP对低温胁迫的缓解效果最佳,当SNP浓度过低和过高时均达不到理想的效果。     

铝肋迫与小麦叶片的内肽酶活性及活性氧的产生

采用温人自然光下小麦种子培养实验，研究了Ａ１＾３＋胁迫下和Ｈ２Ｏ２处理时小麦幼苗叶片中的内肽酶生和可溶性蛋白质的含量变化。结果表明，Ａ１＾３的胁迫和Ｈ２Ｏ２处理均使小麦幼苗叶片中的内肽酶活性升高，可溶性蛋白质含量下降。Ａ１＾３＋的胁迫下，Ｈ２Ｏ２的清除剂ＡＳＡ（抗坏血酸）的加入使仙肽酶活性明显下降，可溶性蛋白质的含量明显增加。Ａ１＾３＋胁迫下小麦幼苗叶片中的仙肽酶活性升高和可溶性蛋白质含量下降的原     

外源NO对NaCl胁迫下山葡萄叶片叶绿素荧光和抗氧化酶活性的影响

为探究NO对山葡萄耐盐性影响的生理机制,以1年生双丰山葡萄扦插苗为试材,采用营养液栽培方法,研究了外源NO供体硝普钠(SNP)处理对50 mmol·L-1 NaCl胁迫下山葡萄叶片叶绿素含量、叶绿素荧光参数和抗氧化酶活性的影响.结果表明,外源NO能显著提升盐胁迫下山葡萄叶片超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性,减少丙二醛(MDA)的产生和积累,保护光合机构免受活性氧伤害,从而提高叶片叶绿素含量;另一方面,外源NO使盐胁迫下山葡萄叶片的PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)、光化学淬灭系数(qP)和保护性热耗散(ΦNPQ)升高,而初始荧光(Fo)和非调节性能量耗散(ΦNO)显著下降,表明外源NO通过保护性热耗散机制缓解盐胁迫引起的光抑制,增强光合电子传递效率,进而维持PSⅡ的正常功能,最终提高了山葡萄耐盐性.     

SA对高温胁迫下葡萄幼苗AsA-GSH循环的影响

本试验以二年生克瑞森无核葡萄为材料,探讨了外源SA对高温胁迫下葡萄体内ASA-GSH循环代谢的影响及其在抗高温胁迫中的作用.试验结果表明,与对照相比,外源SA可以促进高温胁迫下葡萄叶片内ASA和GSH含量的积累量,降低GSSG的含量.长时间(＞240min)的高温胁迫下,外源SA可以降低脱氢抗坏血酸(DHA)的含量;能够维持较高的AsA-GSH循环系统中APX、DHAR、MDHAR、GR活性.外源SA促进了高温胁迫下葡萄ASA-GSH循环的快速而有效的运转,降低了高温胁迫对葡萄植株的氧化伤害,从而缓解了高温胁迫对葡萄幼苗的伤害作用.     

H_2S对低温胁迫下甜樱桃柱头和子房AsA-GSH循环的响应

为了探究H_2S对甜樱桃花器官低温伤害的缓解机理,以甜樱桃品种早大果为试材,分析了不同浓度H_2S供体NaHS对低温胁迫下甜樱桃柱头和子房AsA-GSH循环系统的影响。结果表明,喷施0.02、0.05、0.1 mmol·L~(-1)的NaHS均可降低低温胁迫下甜樱桃柱头和子房超氧阴离子(O_2~-)、过氧化氢(H_2O_2)、丙二醛(MDA)含量,显著提高还原型抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量(P0.05),降低氧化型抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量,使AsA/DHA和GSH/GSSG比值显著升高(P0.05),以0.05 mmol·L~(-1)NaHS效果最显著;0.02、0.05、0.1 mmol·L~(-1)的NaHS均显著提高低温胁迫下柱头和子房AsA-GSH循环中抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)、单脱氢抗坏血酸还原酶(MDAR)、谷胱甘肽还原酶(GR)、谷胱甘肽过氧化物酶(GPX)和谷胱甘肽-S-转移酶(GST)的活性(P0.05),以0.05 mmol·L~(-1)NaHS提高上述酶活性的幅度最大。NaHS的浓度大于0.2 mmol·L~(-1)不再提高低温胁迫下AsA-GSH循环效率;低温胁迫下添加NaHS的同时添加H_2S清除剂HT可解除H_2S的效果。综上所述,喷施适量外源H_2S可有效降低低温胁迫下O_2~-、H_2O,和MDA积累,提高AsA-GSH循环效率,减轻低温对甜樱桃柱头和子房的氧化伤害。本研究结果为明确H_2S缓解甜樱桃花器官低温伤害作用机制以及生产上花期低温伤害预防提供了理论依据。     

外源硫化氢对PEG模拟干旱胁迫下玉米种子萌发及幼苗生长的影响

为明确干旱胁迫下外源硫化氢(H2S)对植物幼苗的缓解作用,以玉米自交系郑58为试验材料,研究了不同浓度(0、0.3、0.6、0.9、1.2及1.5 mmol·L-1)的H2S供体硫氢化钠(Na HS)对15%PEG模拟干旱胁迫下玉米种子萌发的影响,并以筛选到的最佳Na HS浓度对幼苗进行叶面喷施,研究其对幼苗叶片抗氧化酶活性、抗氧化剂含量、游离脯氨酸(Pro)和活性氧(ROS)的积累特征及膜质过氧化水平的影响。结果表明,不同浓度的Na HS处理在一定程度上提高了干旱胁迫下玉米种子的发芽势、发芽率及幼苗的生物量,其中以0.6 mmol·L-1的Na HS处理效果最佳。叶面喷施0.6 mmol·L-1Na HS溶液显著增强了叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)及抗坏血酸过氧化物酶(APX)活性,提高了叶片中抗坏血酸(As A)和谷胱甘肽(GSH)的含量。同时,外源H2S处理增强了玉米叶片中△1-吡咯啉-5-羧酸合成酶(P5CS)的活性,提高了叶片中游离Pro含量,显著降低了叶片中过氧化氢(H2O2)及丙二醛(MDA)含量。综上,外源H2S处理通过提高幼苗的抗氧化水平,减少干旱胁迫对玉米叶片造成的氧化损伤,在一定程度上提高了玉米幼苗对干旱胁迫的适应能力。本研究为进一步探索H2S缓解玉米干旱胁迫的机理提供了理论依据。     

外源抗坏血酸对酸雨胁迫油菜幼苗的缓解效应

为探讨抗坏血酸（AsA）对酸雨胁迫油菜毒害效应的缓解效果,以苏油1号为供试材料,采用盆栽土培的方法研究了不同浓度的外源AsA处理对pH2.5酸雨胁迫下油菜幼苗生长的影响。结果表明,pH2.5酸雨显著抑制了油菜幼苗的生长,喷施外源AsA后,一定浓度范围的AsA可明显缓解油菜的酸雨胁迫,生物量、叶片色素含量、抗氧化酶活性等显著高于酸雨胁迫的油菜,丙二醛（MDA）含量和相对电导率显著低于酸雨处理油菜。但随着AsA喷施浓度的增加,缓解效应下降,生物量、叶绿素含量等下降,而MDA和电导率上升。可见适宜浓度的外源AsA对酸雨胁迫下的油菜幼苗具有一定的缓解效应,但浓度过高则产生促氧化作用,在试验中以4.0 mmol.L-1的效果最佳。     

臭氧对水稻生长的影响及外源抗坏血酸的防护作用

利用开顶式气室研究了臭氧浓度升高对水稻（Oraza sativa L.）生长的影响及外源抗坏血酸（Exogenous Ascorbic Acid）的防护作用。臭氧处理共设4个水平：空气NF（No-Filter,臭氧浓度约20-50 nL·L^-1）、过滤CF（Charcoal-Filter,臭氧浓度约为5-15 nL·L^-1）、臭氧Ⅰ（8 h平均100 nL·L^-1）、臭氧Ⅱ（8 h平均200 nL·L^-1）,外源抗坏血酸浓度设置为0.1％（m/V）。结果表明,与NF处理相比,高浓度O3（200 nL·L^-1）处理会造成水稻叶片的叶绿素a、水稻的株高、叶面积、穗粒数及粒重,分别下降了47.9％、17. 8％、31.6％、45.7％和42.9％;喷施外源抗坏血酸后,与各自的对照相比,以上各生长指标分别上升了11.6％、7.7％、17.4％、5.6%、11.1%。可见外源抗坏血酸能有效缓解O3对水稻的胁迫作用,提高了水稻对O3的抗性,促进水稻的生长。     

Nucleophilic radical substitution reaction of triazine herbicides with polysulfides

Triazine herbicides are among the most widely used herbicides in the United States. Many triazine compounds are relatively stable under natural conditions and have become prominent contaminants in hydrologic systems. It was previously reported that chloro-s-triazine compounds were rapidly dechlorinated in water by polysulfides, and the reaction was assumed to be aromatic nucleophilic substitution (SNAr). In this study, we evaluated the effect of free radical inhibitors on the reaction rate of polysulfides with herbicides atrazine, simazine, and cyanazine. The reaction was significantly inhibited by radical scavengers oxygen and 1,4-benzoquinone, suggesting involvement of free radicals in the reaction. Spectral analysis of the reaction mixture using electron spin resonance showed that after the reaction, the free radical concentration in polysulfide solution substantially decreased. These evidences indicate that radical sulfur anions may also be involved in the reaction, likely via a free radical substitution reaction (SRN1) mechanism. Amendment of sodium tetrasulfide significantly reduced the leaching of atrazine or simazine from packed sand columns. Therefore, polysulfide salts may be potentially used to remove residues of triazine herbicides in environmental media.     

Effect of heat treatment of camelina (Camelina sativa) seeds on the antioxidant potential of their extracts

The effect of different heat treatments of camelina (Camelina sativa) seeds on the phenolic profile and antioxidant activity of their hydrolyzed extracts was investigated. The results showed that total phenol contents increased in thermally treated seeds. Heat treatment affected also the quantities of individual phenolic compounds in extracts. Phenolics in unheated camelina seeds existed in bound rather than in free form. A temperature of 160 °C was required for release of insoluble bound phenolics, whereas lower temperatures were found to be optimal to liberate those present as soluble conjugates. The best reducing power and alkyl peroxyl radical scavenging activity in the emulsion was expressed by phenolics which were bound to the cell wall, whereas the best iron chelators and 2,2-diphenyl-1-picrylhydrazyl (DPPH?) radical scavengers were found to be those present in free form. The heat treatment of seeds up to 120 °C increased the reducing power and DPPH? radical scavenging ability of extracts, but negatively affected iron chelating ability and their activity in an emulsion against alkyl peroxyl radicals.     

外源水杨酸缓解低温胁迫对玉米种子萌发和早期幼苗生长伤害的生理机制

为探讨低温胁迫下外源水杨酸(SA)对植物种子萌发和早期幼苗生长影响的生理机制,本研究以先玉335玉米品种为试验材料,用0.05 mmol·L~(-1)的SA水溶液和去离子水(对照,记作CK)对种子进行浸种处理,研究外源SA对低温胁迫下种子发芽、种胚淀粉酶、氧化损伤水平、抗氧化酶、抗氧化物质和渗透调节物质等的影响。结果表明,与CK相比,SA处理玉米种子的发芽率、发芽指数、活力指数、幼苗干重和鲜重分别显著提高了5.57%、7.20%、23.76%、15.49%和28.52%。SA处理的玉米种胚淀粉酶活性显著提高,在种子萌发第2、第6、第8、第10天比CK提高了28.6%、15.1%、9.6%和16.9%;而超氧阴离子(O_2~)和丙二醛(MDA)含量经SA处理后显著下降。SA处理提高了种胚抗氧化酶的活性,在种子萌发第2、第4、第6和第8天时,超氧化物歧化酶(SOD)活性比CK分别提高了36.6%、25.9%、43.6%和46.3%;过氧化物酶(POD)活性在种子萌发12 d时比CK提高了9.0%;和过氧化氢酶(CAT)活性在第4、第6、第8天时比CK分别提高了13.0%、5.7%和17.0%。此外,SA处理还提高了种胚抗氧化物质还原型谷胱甘肽(GSH)和渗透调节物质脯氨酸、可溶性蛋白和可溶性糖的含量。综上所述,SA可以通过改善渗透调节能力和加速淀粉转化来缓解低温胁迫诱导的氧化损伤。本研究结果为探究SA调控低温胁迫下种子萌发和早期幼苗生长的机制开拓了新视野。     

Identification of radical scavengers in sweet grass (Hierochloe odorata)

Extracts from aerial parts of sweet grass (Hierochloe odorata) were active DPPH free radical scavengers. The active compounds were detected in extract fractions using HPLC with on-line radical scavenging detection. After multistep fractionation of the extract, two new natural products possessing radical scavenging activity were isolated, and their structures were elucidated by NMR and MS. They were identified as 5,8-dihydroxybenzopyranone and 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone. Activities of the compounds isolated were tested by DPPH and ABTS free radical scavenging assays, and compared with the known natural antioxidant rosmarinic acid and Trolox.     

New insights into controversies on the antioxidant potential of the olive oil antioxidant hydroxytyrosol

In the present study, the antioxidant profile of olive oil antioxidants was investigated. Hydroxytyrosol and oleuropein are potent scavengers of hydroxyl radicals (OH*), peroxynitrite (ONOOH), and superoxide radicals (O(2)*(-)). Homovanillic alcohol, one of the main metabolites of hydroxytyrosol, and tyrosol are less potent scavengers of these reactive species. None of the olive oil antioxidants are good hypochlorous acid (HOCl) or hydrogen peroxide (H(2)O(2)) scavengers. Hydroxytyrosol efficiently protects against LDL oxidation in vitro and in vivo. However, no protective effect of hydroxytyrosol is usually demonstrated ex vivo against the oxidation of LDL isolated from humans after hydroxytyrosol consumption. The present study shows that this controversy is due to the isolation of LDL, which greatly reduces the protective effect of hydroxytyrosol against LDL oxidation. Hydroxytyrosol is an efficient scavenger of several free radicals. The physiological relevance of the high intrinsic antioxidant activity of hydroxytyrosol is illustrated by its protection against LDL oxidation.     

Free radical scavenging properties of conjugated linoleic acids.

Conjugated linoleic acids (CLA) were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH.) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR results demonstrated that CLA directly reacted and quenched free DPPH radicals in benzene, while spectrophotometric analysis showed the radical scavenging capacity of CLA in ethanol. Dose and time effects of CLA-DPPH. reactions were observed in both tests. The ED(50) of CLA was 18 mg/mL under experimental conditions. CLA are much weaker radical scavengers as compared to vitamin E, vitamin C, and BHT. Kinetics of CLA-DPPH. reactions was different to that of linoleic acid (LA)-DPPH. reactions. CLA reacted and quenched DPPH radicals at all tested levels without a lag phase, while LA had a lag phase and showed no radical quenching activity at levels of 5-80 mg/mL in 30 min. These data indicated that CLA can provide immediate protection against free radicals, but LA cannot.     

Strawberry and its anthocyanins reduce oxidative stress-induced apoptosis in PC12 cells

Because strawberries are known to contain higher concentrations of phytochemicals and have higher antioxidant capacity among common fruits, their neuroprotective activity was tested in vitro on PC12 cells treated with H2O2. Their protective effect and antioxidant capacity were also compared with those of banana and orange, which are the fresh fruits consumed at highest levels in the United States. The cell viability test using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay showed that strawberry phenolics significantly reduced oxidative stress-induced neurotoxicity. Because oxidative stress is also known to increase neuronal cell membrane breakdown, lactate dehydrogenase (LDH) and trypan blue exclusion assays were also performed. Strawberry showed the highest cell protective effects among the samples. The overall relative neuronal cell protective activity of three fruits by three tests followed the decreasing order strawberry > banana > orange. The protective effects appeared to be due to the higher phenolic contents including anthocyanins, and anthocyanins in strawberries seemed to be the major contributors.     

Antioxidative effect of kaempferol and its equimolar mixture with phenyltin compounds on UV-irradiated liposome membranes

The work investigates the possibility of the protective action of kaempferol on phosphatidylcholine liposome membranes exposed to the pro-oxidative action of diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) induced by UV radiation (lambda = 253.7 nm). The concentrations of kaempferol and its equimolar mixtures with DPhT and TPhT were determined so that they induce 50% inhibition in oxidation of liposomes irradiated with UV. They are 11.6, 10.0, and 4.5 microM/L, which constitute the following sequence of antioxidative activity: kaempferol/triphenyltin > kaempferol/diphenyltin > kaempferol. This relationship is confirmed by the results on the antiradical ability of kaempferol and its mixtures with DPhT and TPhT toward the free radical 2,2-diphenyl-1-picrylhydrazyl. Similar sequences obtained in both studies suggest a possible mechanism of the antiradical action of the mixtures as free radical scavengers. Kaempferol's ability, then documented, to form complexes with phenyltins indicates (a) a possible way to liquidate the peroxidation caused by the free radical forms of phenyltins and (b) the stabilizing role of chelating in the antioxidative action of the kaempferol/phenyltins. The differentiation in the action of the compounds studied may, among others, result from different localizations in the liposome membrane, which is indicated by the results of the fluorometric studies.     

茶树特异成分对辐照诱导自由基的作用

研究了茶树体内特异成分对辐照诱导自由基的作用。结果表明，辐照茶籽内自由基的增长趋势表现为乔木型大叶品种大于灌木型中、小叶品种，１０个品种茶籽内自由基的耗照剂量效应模型为ｙ＝ａｅ（－ｂ／ｘ）。茶树体内儿茶素、茶多酚、黄酮苷、咖啡碱等特异成分与其辐射敏感性及自由基含量变化密切相关。影响辐照茶树体内自由基消长的主要因子是儿茶素，其中（－）－没食子儿茶素没食子酸酯（ＥＧＣＧ）与自由基反应有浓度效应，在低浓度条件下，具有诱发产生自由基的作用，而在高浓度条件下，则有消除自由基的作用     

水分胁迫对巴西香蕉幼苗水分状况、质膜透性和根系活力的影响

在盆栽试验条件下,以巴西香蕉幼苗为试材,设置7个水平土壤含水量处理,分别为100％～91％、90％～81％、80％～71％、70％～61％、60％～51％、50％～41％和40％～0,测定叶片相对含水量、组织含水量、自由水、束缚水含量、质膜透性和根系活力。研究结果表明,随着水分胁迫的加剧,叶片相对含水量、组织含水量、自由水含量和根系活力均随土壤相对含水量的下降而减少;而水分饱和亏缺、束缚水含量和质膜透性则随土壤相对含水量的下降而升高。综合不同处理下巴西香蕉幼苗水分状况、质膜透性和根系活力可知,香蕉幼苗生长最适宜的土壤水分含量是田间持水量的71％～80％。