水杨酸处理诱导采后甜瓜抗坏血酸-还原型谷胱甘肽循环代谢清除过氧化氢的作用及机制

目的：研究抗坏血酸（ascorbic acid，AsA）-还原型谷胱甘肽（reduced glutathione，GSH）循环代谢在水杨酸处理采后甜瓜诱导的过量H2O2清除过程中的作用。方法：用4 mmol/L水杨酸浸泡‘玉金香’厚皮甜瓜10 min，测定处理后果实常温贮藏过程中丙二醛（malondialdehyde，MDA）含量，分析活性氧的积累水平、超氧化物歧化酶（superoxide dismutase，SOD）和过氧化氢酶（catalase，CAT）活力，以及AsA-GSH循环过程相关酶活力及产物和底物含量。结果：水杨酸处理降低了果实MDA含量，第10天处理组MDA含量较对照组降低14.6%；显著提高了果实O2－·的产生速率和H2O2含量（P＜0.05），其中处理后第2天O2－·的产生速率高出同期对照组的1.9 倍，第6天H2O2含量高出对照组果实29.7%；提高了果实SOD活力，但抑制了CAT活力，说明H2O2的清除可能是依赖于除酶促系统外的其他系统。此外，水杨酸处理提高了果实抗坏血酸过氧化物酶、单脱氢抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶和谷胱甘肽还原酶的活力，增加了AsA和氧化型谷胱甘肽的含量，降低了脱氢抗坏血酸和GSH的含量。结论：水杨酸处理诱导了厚皮甜瓜果实的氧爆，抑制了MDA产生，由水杨酸诱导产生的过量H2O2主要依靠AsA-GSH循环系统清除。     

褪黑素对采后荔枝果实冷害及生理变化的影响

以采后“紫娘喜”荔枝果实为试材,使用0.5 mmol/L褪黑素(MT)溶液对其浸泡处理10 min,晾干后置于(4 ± 1) °C、(85 ± 5)%条件下冷藏30 d,研究MT处理对荔枝果实冷害及抗冷相关生理代谢的影响。结果表明,MT处理显著降低了荔枝果实冷害指数,推迟了果皮色度a*值下降;冷害指数在冷藏第30天较对照果实降低49.4%,果皮色度a*值在第10～30天期间平均提高37.2%。MT处理减缓了果实膜相对电导率升高,抑制了丙二醛(MDA)、超氧阴离子(O₂·-)和过氧化氢(H2O₂)积累,如第30天时相对电导率、丙二醛含量、O₂·-生成率和H2O₂含量较对照组分别降低29.6%,16.9%,6.9%和6.3%,从而减轻了果实氧化胁迫并使膜完整性得到维持。MT处理降低了果实多酚氧化酶(PPO)和过氧化物酶(POD)活性,同时提高了总酚、类黄酮和花色素苷含量,导致果实酶促褐变减轻。MT处理提高了果实超氧化物歧化酶(SOD)、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)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)等抗氧化酶的活性,维持了较高的抗坏血酸(AsA)和还原性谷胱甘肽(GSH)含量及AsA/脱氢抗坏血酸(DHA)和GSH /氧化型谷胱甘肽(GSSG)比值,从而增强了冷藏荔枝果实的抗氧化活性。此外,MT处理促进了冷藏期间荔枝果实LcMsrA1、LcMsrA2、LcMsrB1和LcMsrB2上调表达,进而改善了果实蛋白质氧化损伤修复能力。结论:外源MT处理可通过调节冷藏荔枝果实抗冷相关生理代谢使果实冷害得到缓解。     

BTH处理对采后草莓果实还原势和抗病性的调控作用

为明确苯丙噻唑硫代乙酸甲酯(BTH)处理抑制草莓果实采后灰霉病的相关机理,本研究分析了BTH对果实在20 ℃贮藏期间还原势及抗病性的调控作用。结果显示,单一BTH处理在贮藏1 d后可有效诱导草莓果实磷酸戊糖代谢途径关键酶G6PDH(葡萄糖-6-磷酸脱氢酶)、6PGDH(6-磷酸葡萄糖酸脱氢酶)活性以及AsA-GSH(抗坏血酸-谷胱甘肽循环)循环关键酶MDHAR(单脱氢抗坏血酸还原酶)、DHAR(脱氢抗坏血酸还原酶)、GR(谷胱甘肽还原酶)和APX(抗坏血酸过氧化物酶)活性的上升,促进NADPH(还原型烟酰胺腺嘌呤二核苷酸磷酸)、GSH(还原型谷胱甘肽)和AsA(抗坏血酸)等还原性物质含量的上升,并抑制NADP+(烟酰胺腺嘌呤二核苷磷酸)、GSSG(氧化型谷胱甘肽)和DHA(脱氢抗坏血酸)等氧化产物的合成,从而提高果实内部还原势;伴随着还原势的升高,果实中FaPR1、FaPR5、FaCHI-1和Faβglu等PRs基因表达丰度出现明显的上升趋势,同时果实由Botrytis cinerea导致的灰霉病发病率显著(p<0.05)降低。另一方面,经BTH处理的果实在接种病原菌B. cinerea后,其果实内PPP(磷酸戊糖)途径和AsA-GSH循环关键酶活性以及PRs基因表达丰度在整个贮藏期间出现较单一BTH处理更为显著的提高(p<0.05),同时果实发病率和病斑直径也显著下降(p<0.05)。这些结果说明,0.1 mmol/L BTH可通过诱导Priming抗性,使草莓果实在受到B. cinerea侵染时产生强烈抗病性;同时,BTH处理可提高PPP途径和AsA-GSH循环关键酶活性,促进果实中还原性物质积累,从而为PRs基因表达提供高还原势的有利环境。     

外源钙和钙调素拮抗剂对冷藏桃果实耐冷性的影响

以‘白凤’水蜜桃为试材,分别用外源钙（CaCl2）和钙调素拮抗剂三氟拉嗪（trifluoperazin,TFP）浸泡桃果实,以蒸馏水为对照,研究其对冷藏桃果实抗冷性的影响。结果表明：与对照组相比,CaCl2处理能有效减轻桃果实果心褐变程度,缓解冷害症状,降低相对电导率,降低丙二醛（malondialdehyde,MDA）、H2O2含量,降低超氧阴离子自由基（O2 － ·）产生速率以及脯氨酸脱氢酶（proline dehydrogenase,PDH）活力,提高活性氧代谢相关酶（超氧化物歧化酶（superoxide dismutase,SOD)、过氧化氢酶（catalase,CAT）、抗坏血酸过氧化物酶（ascorbate peroxidase,APX）、Δ1-吡咯啉-5-羧酸合成酶（Δ1-pyrroline-5-carboxylate synthetase,P5CS）、鸟氨酸氨基转移酶（ornithine δ-aminotransferase peroxidase,OAT）、谷胱甘肽还原酶（glutathione reductase,GR））活力;另外,CaCl2处理后的桃果实表现为较高的脯氨酸、VC和谷胱甘肽（glutathione,GSH）含量;而TFP处理后的桃果实冷藏特性与CaCl2处理组相反。这说明钙-钙调素（Ca2＋-CaM）复合体参与了采后桃果实抗冷性调控,Ca2＋浓度的增加能维持桃果实活性氧代谢平衡,减少低温胁迫下膜脂过氧化与损伤,增加渗透调节物质脯氨酸的积累,从而减少桃果实冷藏期间冷害的发生,保持果实营养品质,延长果实贮藏时间。     

采后ASM处理对苹果果实抗坏血酸-谷胱甘肽循环系统的影响

采后100mg·L-1的苯丙噻重氮(ASM)溶液浸泡苹果果实10min,24h后损伤接种P.expansum,测定常温贮藏期间果实病斑直径及抗坏血酸-谷胱甘肽循环系统的变化。结果表明,ASM处理显著降低了果实病斑直径,并提高了果实过氧化氢(H2O2)含量,抑制了过氧化氢酶(CAT)活性,提高了果实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(MDAR)、脱氢抗坏血酸还原酶(DHAR)活性及抗坏血酸(As A)和还原型谷胱甘肽(GSH)含量。由此表明,ASM处理通过抑制CAT活性促进果实前期H2O2的积累,从而启动果实体内其他防卫反应提高抗病性,抗坏血酸-谷胱甘肽循环系统中抗氧化酶活性和抗氧化剂含量的提高有利于消除过量的H2O2对果实的伤害。     

采后蛋氨酸处理对桃果实青霉病及活性氧代谢的影响

以桃果实为材料,研究了采后不同浓度蛋氨酸处理对损伤接种桃果实扩展青霉(Penicillium expansum)病斑扩展的影响,根据病斑直径的大小筛选出能够有效抑制桃果实青霉病的最佳浓度,并以最佳浓度处理桃果实分析对活性氧代谢的影响。结果表明,15 mmol/L蛋氨酸对P.expansum的抑制效果最好,并且处理显著(p≤0.05)提高了桃果实中抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量;谷胱甘肽还原酶(GR)活性、抗坏血酸过氧化物酶(APX)活性和过氧化氢酶(CAT)活性也显著提高,同时提高了H_2O_2含量。由此表明,采后蛋氨酸处理可以通过调节桃果实体内活性氧代谢来提高果实对青霉病的抗性。     

基于S-亚硝基化解析一氧化氮对哈密瓜采后抗环血酸-谷胱甘肽循环的影响

为了探究一氧化氮(NO)对哈密瓜采后贮藏期的抗氧化作用，该研究以“西州蜜17”为试材，采用外源NO精准熏蒸方法，分析测定哈密瓜生理指标、S-亚硝基化水平和抗氧化指标的变化，从S-亚硝基化水平的角度探讨NO对哈密瓜采后抗坏血酸-谷胱甘肽循环(glutathione-ascorbate cycle, AsA-GSH cycle)的影响。结果表明，NO熏蒸能较好地维持哈密瓜贮藏品质，降低果实H₂O₂、丙二醛(malondialdehyde, MDA)含量，显著提高果实内源NO和S-亚硝基硫醇(S-nitrosothiols, SNO)含量，抑制S-亚硝基谷胱甘肽还原酶(S-nitrosoglutathione reductase, GSNOR)活性升高。NO熏蒸可以维持较高的抗坏血酸(ascorbic acid, AsA)和脱氢抗坏血酸(dehydroascorbate, DHA)的比值(AsA/DHA)、还原型谷胱甘肽(reduced glutathione, GSH)和氧化型谷胱甘肽(oxidized glutathione, GSSG)的比值...     

一氧化氮对采后水蜜桃果实衰老和清除自由基酶系影响

为研究一氧化氮(NO)处理对采后水蜜桃果实衰老和清除自由基相关酶的影响,分别采用0、5、10、20和30μL/L的NO气体熏蒸水蜜桃,然后置于20℃下贮藏10 d。结果表明:10μL/L的NO处理可有效地抑制水蜜桃果实软化。对自由基清除酶系影响研究表明,NO处理提高了贮藏期果实超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)和单脱氢抗坏血酸还原酶(MDHAR)活性,保持了较高抗坏血酸(ASC)含量。因此,适宜浓度(10μL/L)的NO处理能提高桃果实清除自由基酶系能力,抑制膜脂过氧化并保持细胞膜完整性,进而改善贮藏品质。     

无硫复合护色剂对冷藏桃抗氧化酶活力的影响

为探讨无硫复合护色剂减轻冷害的效果,以"水蜜桃"为试材,试验共设3组:非处理桃(阴性对照)、无硫复合护色剂处理桃和1-MCP处理桃(阳性对照),经40 d冷藏后,测定桃果肉中VC、多酚和抗氧化酶的水平和活力。结果表明,与非处理对照组相比,无硫复合护色剂处理下冷藏桃果实的VC含量、多酚水平和抗氧化酶活力,包括超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、多酚氧化酶(PPO),均维持较高水平;丙二醛水平和过氧化物酶(POD)活性均显著较低。从指标分析来看,无硫复合护色剂在维持抗氧化酶活力和抑止褐变的作用效果优于1-MCP。试验表明无硫复合护色剂处理可通过维持较高的抗氧化酶活力、降低氧化应激和多酚氧化,从而有利于减轻桃果实冷害的发生和果肉的褐变。     

水杨酸处理对杏果实冷害及活性氧代谢的影响

以新疆塞买提杏为实验材料,用质量浓度0.01 g/L的水杨酸以减压渗透方式处理,置于温度0 ℃、湿度90%～95%的冷库贮藏。定期测定杏果实冷害指数和冷害发病率及与活性氧代谢相关的超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）、超氧阴离子自由基（O2－·）的产生速率以及过氧化氢（H2O2）的含量。结果表明：质量浓度0.01 g/L的水杨酸处理能明显降低杏果实冷害发生率,减缓杏果实贮藏期间CAT和POD活性的下降,有效提高杏果实SOD的活性,抑制O2－·产生速率和H2O2含量的增长。说明水杨酸处理可减轻杏果实的冷害发病率,这与水杨酸处理能防止杏果实冷藏期间过高的氧化伤害,维持杏果实活性氧代谢平衡密切相关。     

γ-Aminobutyric acid treatment reduces chilling injury and activates the defence response of peach fruit

Peach fruit were immersed in 5 mM γ-aminobutyric acid (GABA) solution for 10 min at 20 °C and then stored at 1 °C for 5 weeks to investigate the effect of GABA treatment on chilling injury (CI), antioxidant enzymes and energy status in peach fruit. The results showed that GABA treatment significantly inhibited CI incidence of peaches and enhanced activities of antioxidant enzymes, such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione S-transferase, monodehydroascorbate reductase and dehydroascorbate reductase. The treatment also increased contents of adenosine triphosphate and adenosine diphosphate, but lowered adenosine monophosphate content, which resulted in a higher level of energy charge in treated fruit. These results indicated that GABA increased chilling tolerance of peach fruit through enhancing its enzymatic antioxidant system and maintaining energy status in peach fruit.     

Soluble Sugar Content and Metabolism as Related to the Heat-Induced Chilling Tolerance of Loquat Fruit During Cold Storage

The effects of high-temperature, short-time hot air treatment (45 °C for 3 h) on soluble sugar metabolism and chilling tolerance in loquat fruit stored at 5 °C for 5 weeks were investigated. Heat treatment significantly reduced chilling severity, as evidenced by lower firmness and internal browning and higher levels of extractable juice. Meanwhile, this treatment accelerated the activities of acid invertase, neutral invertase, sucrose phosphate synthase and sucrose synthase during storage. However, sucrose degradation was predominant, which caused lower levels of sucrose and higher levels of glucose and fructose in the heat-treated group. In addition, the ascorbate acid content and the activities of ascorbate peroxidase and glutathione reductase in the heat-treated fruit were much higher than those in control fruit, resulting in lower levels of hydrogen peroxide (H₂O₂) and malondialdehyde and decreased membrane permeability as well as a higher unsaturated/saturated fatty acid ratio at the end of storage. Our results suggest that the increased levels of reducing sugars, especially those of glucose, may induce the ascorbate–glutathione cycle activity to scavenge for H₂O₂, whose content relates to the heat-induced chilling tolerance of loquat fruit.     

Effect of 1-methylcyclopropene on chilling injury and quality of peach fruit during cold storage

The effects of different concentrations (0, 0.1, 0.5, 1, and 5 μL/L) of 1-methylcyclopropene (1-MCP) on chilling injury (CI), fruit quality, and antioxidant enzyme activities in cold-stored peach fruit (Prunus persica Batsch cv Baifeng) were investigated. The results showed that treatment with 0.5 μL/L 1-MCP significantly alleviated CI symptoms, including internal browing (IB) and flesh mealiness (FM), and maintained higher fruit quality. In addition, 1-MCP inhibited the activities of polyphenol oxidase (PPO) and peroxidase (POD), maintained higher activities of antioxidant enzymes and kept the balance of the polygalacturonase (PG)/pectinmethylesterase (PME) ratio. The treatment of 1-MCP markedly inhibited the increase of electrolyte leakage and the accumulation of malondialdehyde and hydrogen peroxide. Thus, 1-MCP (0.5 μL/L) treatment is effective in preventing CI and maintaining overall quality in peach fruit. The effect of 1-MCP on alleviating CI may be due to its capability to enhance antioxidant enzyme activities and to reduce oxidative damage. Practical Application: Treatment with 0.5 μL/L 1-MCP significantly prevented chilling injury and maintained fruit quality in "Baifeng" peaches. In addition, 1-MCP could enhance antioxidant enzyme activities and alleviate oxidative damage. Thus, 1-MCP has the potential for application in the Asiatic peach industry.     

Maturity‐dependent chilling tolerance regulated by the antioxidative capacity in postharvest cucumber (Cucumis sativus L.) fruits

BACKGROUND: The aim of the present study was to reveal the effect of fruit maturity on the chilling tolerance of cucumber (Cucumis sativus L.) fruit and the oxidative and antioxidative mechanisms involved. Chinese mini‐cucumber (cv. Hangcui‐1) fruits were harvested at four developmental stages: Immature (3–8 days after anthesis (DAA)), Mature (9–16 DAA), Breaker (17–22 DAA) and Yellow (35–40 DAA). All fruits were stored at 2 °C for 9 days and rewarmed at 20 °C for 2 days. RESULTS: The chilling injury index declined with advancing fruit maturity. High superoxide anion radical production rate and hydrogen peroxide content were observed in Immature fruits after cold storage and rewarming. Under chilling stress, superoxide dismutase showed an early response. Fruits at earlier maturity stages exhibited higher catalase, ascorbate peroxidase and monodehydroascorbate reductase activities and glutathione content as well as its redox state, and lower peroxidase, dehydroascorbate reductase and glutathione reductase activities and ascorbate content as well as its redox state. CONCLUSION: Fruits at the earlier developmental stage are more susceptible to chilling injury, which is related to increased oxidative stress. High peroxidase activity and ascorbate content and maintenance of the latter's redox state appear critical to the chilling tolerance of cucumber fruits at later developmental stages. © 2012 Society of Chemical Industry     

高湿贮藏对青椒果实冷害和抗氧化活性的影响

为探究高湿贮藏对减轻青椒果实冷害的作用及其与抗氧化活性的关系,将青椒果实放置于4 ℃、相对湿度分别为96%～99%和70%～75%的干雾控湿高湿冷库和普通低湿冷库中贮存15 d,每3 d测定果实冷害、品质和抗氧化系统相关指标变化。结果表明,高湿贮藏可显著延缓青椒果实的冷害指数、相对电导率和质量损失率的上升及硬度的下降,保持较高的叶绿素、抗坏血酸、总酚和总黄酮含量。与低湿贮藏相比,高湿贮藏还可显著提高超氧化物歧化酶、过氧化氢酶、过氧化物酶和抗坏血酸过氧化物酶的活力,保持较高的1,1-二苯基-2-三硝基苯肼和羟自由基清除率,减少超氧阴离子和过氧化氢的积累。这些结果表明,高湿贮藏可维持青椒果实较高的抗氧化活性,从而抑制活性氧对青椒的伤害,减少果实冷害的发生。     

Effect of cold‐shock treatment on chilling injury in mango (Mangifera indica L. cv. ‘Wacheng’) fruit

To investigate how cold shock may affect chilling injury in mango fruit (Mangifera indica L. cv. ‘Wacheng’), the fruit were treated for 3, 4 or 5 h at 0 °C, or treated for 8, 10 or 12 h at 4 °C, respectively, then transferred to 20 °C for 20 h prior to being stored at 2 °C, 85–95% RH. The chilling injury index of mango treated at 0 °C for 4 h was 59.7% lower than that of the control fruit directly stored at 2 °C, 85–95% RH. Some attributes were assayed in the fruit treated at 0 °C for 4 h. Ion leakage of the cold‐shock fruit at 0 °C for 4 h was 16% or 10% lower than that of the control on day 9 or day 12 of storage, respectively. Malondialdehyde content of the cold‐shocked fruit was 70% or 50% lower than that of the control on day 6 or day 12 of storage at 2 °C, respectively. Activities of catalase, ascorbate peroxidase, and contents of glutathione and phenolic compounds in the fruit during storage were all markedly enhanced by the cold‐shock treatment, whereas activities of superoxide dismutase, glutathione reductase and content of ascorbic acid in the mango were slightly influenced by the cold‐shock treatment. These results suggest that cold‐shock treatment may hold promise as an alternative approach to reduce chilling injury in mango fruit during cold storage. Copyright © 2006 Society of Chemical Industry     

枇杷果实热水和甜菜碱复合处理保鲜条件优化

以“解放钟”枇杷果实为试材,采用响应面试验研究不同的热水处理温度（40、45、50 ℃）、时间（5、10、15 min）以及不同浓度甜菜碱（5、10、15 mmol/L）对1 ℃冷藏枇杷果实品质的影响。通过对枇杷果实果心褐变指数、出汁率和硬度的测定,建立这3 个响应值的二次多项模型,分析其拟合度,并进行验证分析,同时利用模型的响应面对影响枇杷果实品质的关键因素及其相互作用进行探讨。结果表明,甜菜碱结合热处理降低采后枇杷冷害的最优条件为：处理温度44.36 ℃、时间9.14 min、甜菜碱浓度10.65 mmol/L。验证实验结果表明,该复合处理组褐变指数、出汁率、硬度分别为23.66%、58.91%、2.66 N,能有效抑制枇杷果实冷害症状,保持较好品质,且处理效果优于单独处理。     

Fatty acid composition and antioxidant system in relation to susceptibility of loquat fruit to chilling injury

Two cultivars of loquat fruit with contrasting chilling resistance were stored at 1 °C for 35 days to investigate the relationship between chilling injury and fatty acid composition and its antioxidant system. No symptoms of chilling injury occurred in the fruit of ‘Qingzhong’ cultivar during the whole storage, whereas in ‘Fuyang’ fruit, chilling injury increased sharply after 21 days of storage at 1 °C. ‘Qingzhong’ fruit had lower levels of superoxide radical and H₂O₂, in addition to lower lipoxygenase activity, but higher membrane lipid unsaturation and higher activities of superoxide dismutase and catalase than ‘Fuyang’. Furthermore, the chilling resistant ‘Qingzhong’ fruit also showed higher activities of antioxidant enzymes involved in ascorbate–glutathione cycle and higher levels of ascorbate acid and reduced glutathione. These results suggest that the higher membrane lipid unsaturation and the more efficient antioxidant system were both beneficial in enhancing resistance of loquat fruit to chilling injury.