Antioxidative activity associated with chilling injury tolerance of muskmelon (Cucumis melo L.) rind

‘Galia’ melon (Cucumis melo L. var. reticulatus) is a climacteric fruit with a short storage life. To prevent over-ripening, fruits are stored at 4–6 °C, which also results in chilling injury (CI) that appears as numerous brown spots on the surface of the fruit. It has been suggested that exposure of ‘Galia’ fruits to high growth temperatures in the field renders them sensitive to low storage temperatures. Activity profile of the antioxidative enzymes catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) was monitored in the rind of ‘Galia’ fruits during low-temperature storage, to associate each enzyme's activity with CI incidence. Experiments were performed with low-temperature-sensitive and tolerant varieties, 5080^S and 1537^T respectively, and included a pre-storage treatment of hot-water wash of 5080^S fruits.     

Induction of disease resistance and ROS metabolism in navel oranges by chitosan

The objective of this work was to evaluate how disease resistance and reactive oxygen species (ROS) metabolism in harvested navel oranges (Citrus sinensis L. Osbeck) may be affected by chitosan. Fresh navel oranges were treated with 2% chitosan or 0.5% glacial acetic acid (control) solution for 1 min, and some were inoculated with Penicillium italicum and Penicillium digitatum. Then, the fruit were stored at 20 °C and 85–95% RH. Treatment with 2% chitosan significantly reduced the disease incidence and the lesion diameter compared with control fruit. This treatment effectively enhanced the activities of peroxidase (POD) and superoxide dismutase (SOD), and levels of glutathione (GSH) and hydrogen peroxide (H₂O₂), inhibited the activities of catalase (CAT) and the decreases of ascorbate (AsA) content during navel orange fruits storage. Ascorbate peroxidase (APX) activity in the navel orange fruit was induced slightly by the chitosan treatment during 14–21 days storage. However, glutathione reductase (GR) activity in the fruit was not enhanced by the chitosan treatment. These results indicated that chitosan treatment could induce the navel orange fruit disease resistance by regulating the H₂O₂ levels, antioxidant enzyme and ascorbate–glutathione cycle.     

Changes in antioxidants and fruit quality in hot water-treated ‘Hom Thong’ banana fruit during storage

The effects of hot water treatment on antioxidants and fruit quality were investigated in banana fruit of cv. Gros Michel (Musa acuminata, AAA Group, locally called cv. Hom Thong) by immersing fruits in hot water (50 °C) for 10 min, before storage at 25 °C for 10 days or 14 °C for the first 8 days followed by storage at 25 °C for the second 8 days until ripening. Quality parameters including peel color and pulp firmness indicated that hot water treatment helped to delay banana fruit ripening at both storage conditions. Hot water treatment decreased the levels of hydrogen peroxide (H₂O₂) and malonydialdehyde (MDA) during storage at 25 °C. Glutathione (GSH and GSSG) contents and the ratio of GSH/GSSG during fruit approaching ripening were significantly induced in hot water-treated fruits while ascorbic acid (AA) contents were slightly increased. In addition, the combined treatment increased free phenolics and flavonoids during storage. Results suggest that hot water treatment has led to an induction of antioxidants in banana fruits as indicated by an increase of antioxidants and a decrease of H₂O₂ during ripening, and all of which result in a delayed ripening of banana fruit.     

Hydrogen peroxide pretreatment alters the activity of antioxidant enzymes and protects chloroplast ultrastructure in heat-stressed cucumber leaves

To elucidate the physiological mechanism of heat stress mitigated by exogenous hydrogen peroxide (H₂O₂) further, seedlings of Cucumis sativus cv Lvfeng no. 6 were subjected to two temperatures (42/38 and 25/18 °C) after pretreatment with 1.5 mM H₂O₂. We investigated whether exogenous H₂O₂ could protect chloroplast ultrastructure under heat stress (42/38 °C) and whether the protective effect was associated with the regulation of antioxidant enzymes. The heat condition disintegrated the membranes of 71.4% chloroplasts in the leaf cells and resulted in the elevated levels of malondialdehyde (MDA) and endogenous H₂O₂. When H₂O₂ pretreatment was combined with the heat stress, the abnormal chloroplasts occurred at a rate of 33.3%, and the contents of MDA and endogenous H₂O₂ were decreased. Heat stress and exogenous H₂O₂ both increased the activities of antioxidant enzymes such as glutathione peroxidase (GSH-Px, EC 1.11.1.9), dehydroascorbate reductase (DHAR, EC 1.8.5.1), monodehydroascorbate reducatase (MDHAR, EC 1.6.5.4), and glutathione reductase (GR, EC 1.6.4.2). The combined effect of heat stress and H₂O₂ pretreatment led to higher activity of antioxidant enzymes including superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), GSH-Px, DHAR, MDHAR and GR in comparison to the heat treatment alone. We propose that exogenous H₂O₂ increases antioxidant enzyme activities in cucumber leaves, decreases lipid peroxidation, and thus protects the ultrastructure of chloroplasts under heat stress.     

Effect of silicon on antioxidant and stomatal response of two grapevine (Vitis vinifera L.) rootstocks grown in boron toxic,saline and boron toxic-saline soil

We investigated individual and combined effects of B toxicity and salinity in the presence or absence of silicon on the shoot growth, concentrations of sodium (Na), chloride (Cl), boron (B) and silicon (Si), and stomatal resistance (SR), lipid peroxidation (MDA), proline accumulation, H₂O₂ accumulation and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) activity grapevine rootstocks of 41B (V. Vinifera × V. Berlandieri) and 1103P (V. Berlandieri × V. Rupestris). Applied Si counteracted the deleterious effects of salinity and boron toxicity on shoot growth by lowering the accumulation of Na in 1103P, and B and Cl in the both rootstocks. Stomatal resistance, MDA, and the concentrations of H₂O₂ and proline were higher in the plants grown in conditions of B toxicity, salinity and their combination while applied Si lowered these parameters. Lowering SOD and CAT but increasing APX, Si treatment significantly affected the enzyme activities of both rootstocks. Based on the present work, it can be concluded that Si alleviates the adverse effects of salinity, B toxicity and combined salinity-B toxicity on grapevine rootstocks by preventing both oxidative membrane damage and translocation of Na and B from root to shoots and/or soil to plant, and also lowering the phytotoxic effects of Na and B within plant tissues. When considering the antioxidative response and membrane systems, it was concluded that the rootstock 1103P was responsive to Si under stress conditions. To our knowledge, this is the first report that Si improves the combined salt and B tolerance of grapevine grown under saline, B toxic, and B toxic and saline conditions which describes membrane related parameters and antioxidant responses.     

Characterization of blueberry monodehydroascorbate reductase gene and changes in levels of ascorbic acid and the antioxidative capacity of water soluble antioxidants upon storage of fruits under various conditions

Blueberry (Vaccinium corymbosum) is among the richest fruits in ascorbic acid (AA), which is the most important antioxidant involved in the ascorbate–glutathione cycle. In this cycle monodehydroascorbate reductase (MDAR) is the enzymatic component involved in the regeneration of reduced ascorbate. Here we report on the isolation of a full-length cDNA from blueberry encoding a protein of 433 amino acids homologous to the MDARs of Pisum sativum and Vitis vinifera. To assess changes in the expression of blueberry MDAR after harvest, a storage trial was initiated, and the major results were: (1) A dramatic loss in AA occurred under all storage conditions. However, storing fruit under low O₂, combined with high CO₂ level (up to 18%) resulted in better preservation of AA. (2) The antioxidative capacity of water soluble antioxidants (ACW) decreased under all storage conditions, even after 3 weeks storage time, and decreasing O₂ levels did not result in preservation of the ACW. The northern blot hybridization showed a clear differential expression between freshly harvested and stored fruits as well as between fruits stored under various storage condition, in accordance with the above-mentioned changes.     

Peroxidase activity in avocado fruit stored at chilling temperatures

No increase in peroxidase activity was observed in ‘Fuerte’ avocado fruits which showed chilling injury symptoms as a result of storage at 0 or 2°C. Peroxidase activity in the fruit declined along with fruit softening during the ripening process. It is suggested that peroxidase acitivity in avocado fruit mesocarp has no role in the development of the chilling injury disorder appearing as dark patches on the skin of the fruit.     

Putrescine and carnauba wax pretreatments alleviate chilling injury,enhance shelf life and preserve pomegranate fruit quality during cold storage

Keeping in mind to reduce chilling injury and retain quality; pomegranate (Punica granatum L., cv. Mridula) fruits were treated with putrescine, carnauba wax and putrescine + carnauba wax prior to cold storage at 2 °C. Before analyzing physical, physiological and biochemical parameters fruits were subjected to post cold storage exposure at 20 °C for 3 days. Untreated fruits developed rapidly chilling injury, with main symptoms being brown discolouration of the skin, surface pitting, weight and firmness loss during storage. All these undesirable changes were significantly delayed by putrescine + carnauba wax application. Respiration and ethylene evolution rate were also brought down by combined application of putrescine and carnauba wax treatment. The superiority of combine treatment over other applications seems arises due to additive benefit of antisenescence and barrier properties of putrescine and carnauba wax, respectively.     

Changes in antioxidative system and membrane damage of lettuce in response to salinity and boron toxicity

Individual and combined effects of salinity and B toxicity on growth, the major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX) activities, ascorbic acid, proline, and H₂O₂ accumulation, and stomatal resistance (SR), malondialdehyde (MDA), membrane permeability (MP) and the concentrations of sodium (Na), chloride (Cl) and boron (B) of lettuce were investigated. Boron toxicity and salinity reduced growth of lettuce plants. Under B toxicity, B concentration of the plants was increased, but in the presence of NaCl, the concentration of B was significantly reduced. Sodium and Cl concentrations were increased in B + NaCl and NaCl treatments. Membrane damage was more pronounced in NaCl and B + NaCl treatments. Stomatal resistance of the plants was significantly increased by salinity treatments. The accumulation of proline and ascorbic acid was the highest in the B + NaCl treatment. In general, stress conditions significantly increased H₂O₂ and antioxidant enzyme (SOD, CAT and APX) activities. The present results indicate that stomatal closure is an important response of lettuce against NaCl and B + NaCl stress. Furthermore NaCl and B + NaCl toxicity-induced oxidative stress in lettuce resulting in lipid peroxidation and membrane damage. Increased antioxidant enzyme activities and also accumulation of ascorbic acid and proline are involved in order to overcome B- and NaCl-induced oxidative stress.     

Magnesium deficiency induced oxidative stress and antioxidant responses in mulberry plants

The aim of the study was to implicate induction of oxidative stress and antioxidative responses with the effects of Mg deficiency in mulberry plants. Mulberry (Morus alba L.) cv. Kanva-2 plants grown in hydroponics were subjected to deficiency of Mg. Mg-deficient plants developed visible symptoms—deep interveinal chlorotic mottling and necrosis in the older and middle leaves. The decreases in the dry matter yield of plants and concentrations of sugars and starch in the leaves of Mg-deficient plants are suggestive of decreased photosynthetic activity. Mg-deficiency decreased concentrations of photosynthetic pigments, and increased concentrations of H₂O₂ and ascorbate and activities of antioxidative enzymes—peroxidase (POD), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The results suggest induction of oxidative stress by enhancing generation of ROS and inducing alterations in redox status, accompanied by activation of antioxidant machinery including induction of some new SOD isoforms in Mg-deficient mulberry plants. Despite significant increase in H₂O₂, lipid peroxidation was decreased in Mg-deficient plants.     

New Approaches to Modeling Methyl Jasmonate Effects on Pomegranate Quality during Postharvest Storage

Adaptive neuro fuzzy inference system (ANFIS) and genetic algorithm–artificial neural network (GA-ANN) models were used to predict the effect of methyl jasmonate (at three levels 0, 0.01, and 0.1 mM) and storage time (0, 14, 28, 42, 56, 70, and 84 days) on quality parameters and physiological changes of pomegranate fruits during storage. Methyl jasmonate reduced chilling injury and improved quality characteristics of pomegranates during postharvest storage. The GA-ANN and ANFIS were fed with two inputs of methyl jasmonate and storage time. The results showed that GA-ANN predictions agreed with experimental data and the GA-ANN with 14 neurons in one hidden layer can predict physiological changes and quality parameters of pomegranate (weight loss, pH, chilling injury index, ion leakage, ethylene, respiration, polyphenols, anthocyanins, and total antioxidant activity) with correlation coefficients equal to 0.87. The ANFIS model was trained by a hybrid method and agreement between experimental data and ANFIS predictions was significant (r = 0.90).     

杧果采前喷施茉莉酸甲酯对其抗病性和采后品质的影响

 以‘台农1号’杧果（Mangifera indica L.‘Tainong 1’）为试材,研究了采前喷施茉莉酸甲酯（MeJA）处理对杧果抗病性和采后品质的影响及其相关机理。结果表明,与对照果实相比,50 μmol · L^-1 MeJA采前处理显著降低了采收时的病果率和贮藏期的病情指数,抑制了接种炭疽病菌果实的病斑直径;有利于杧果贮藏品质的保持,提高了果肉中维生素C含量,延缓了可溶性糖含量的升高和可滴定酸含量的降低;同时,采前MeJA处理可以提高杧果果皮中苯丙氨酸解氨酶（PAL）、过氧化物酶（POD）、多酚氧化酶（PPO）和β–1,3–葡聚糖酶（GLU）等防御酶的活性,提高贮藏早期的过氧化氢（H₂O₂）水平,抑制贮藏后期H₂O₂和MDA含量的积累。这些结果表明,采前MeJA处理提高杧果抗病性和保持果实品质与激活杧果的防御系统及降低膜脂过氧化程度有关。     

草酸处理对采后猕猴桃冷害、抗氧化能力及能荷的影响

‘华优’猕猴桃(Actinidia chinensis ‘Huayou’)果实采收后用5 mmol·L~(-1)草酸浸泡10 min,置于(0±0.5)℃,RH 90%~95%的冷库贮藏90 d。结果发现,草酸处理能够缓解猕猴桃果实的冷害和细胞膜损伤,延缓硬度、可滴定酸的下降,显著提高超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,维持较高的抗坏血酸(AsA)及谷胱甘肽(GSH)含量,降低超氧阴离子自由基生成速率(O_2~-)和过氧化氢(H~2O~2)含量,维持较高的ATP含量及能荷水平,表明草酸处理能保持良好的果实品质,增强果实的抗冷性,可能与提高果实的抗氧化能力,维持较高的ATP和能荷有关。     

Improvement of internal color of oranges stored in oxygen-enriched atmospheres

‘Hamlin’, ‘Parson Brown’ and ‘Pineapple’ oranges were stored for 4 weeks at 15°C in a continuous flow of (1) air, (2) 20 mg 1^?1 ethylene (C₂H₄) in air, (3) 40% O₂ + 60% N₂, or (4) 80% O₂ + 20% N₂, followed by 2 additional weeks in air. Fruits stored in the C₂H₄ atmosphere lost rind chlorophyll faster, and the rind turned orange quicker, than fruits in the other atmospheres. However, most of the fruits stored in the C₂H₄ atmosphere had paler endocarp and juice than fruits stored in the other atmospheres. Fruits stored in 80% O₂ had the palest rind, but their endocarp and juice color were the deepest orange. Color change was detectable after 2–3 weeks and continued to develop until the end of the experiments. In 40% O₂ fruit, response was intermediate.The respiration rate of ‘Pineapple’ oranges during 4 weeks of storage in the test atmospheres was highest in the fruits stored in C₂H₄, almost as high in fruits stored in 80% O₂, and lowest in fruits kept in 40% O₂ or in air. Fruits stored in the different atmospheres did not differ significantly in total soluble solids content, total acidity, or pH of the juice, and the atmospheres did not adversely affect the flavor of the juice.     

Exogenous paraquat changes antioxidant enzyme activities and lipid peroxidation in drought-stressed cucumber leaves

In order to examine whether paraquat modifies the functioning of antioxidants and oxidative stress levels in drought-stressed plants, a cucumber cultivar (Cucumis sativus cv. Yuexiu no. 3) was grown hydroponically for 2 days. Drought stress, which was induced by polyethylene glycol (PEG), increased the contents of malonaldehyde (MDA), superoxide radical (O₂⁻) and hydrogen peroxide (H₂O₂) in cucumber leaves, while pretreatment of paraquat decreased them. Under drought stress induced by PEG, we observed the decreased contents of MDA, H₂O₂ and O₂⁻ in paraquat-pretreated plants in comparison to unpretreated stressed plants. Drought stress and paraquat both increased the activities of antioxidants such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), monodehydroascorbate reducatase (MDHAR, EC 1.6.5.4), glutathione reductase (GR, EC 1.6.4.2), reduced glutathione (GSH) and reduced ascorbate (AsA). But the combined effect of paraquat application and drought stress resulted in the highest activities of antioxidants. So paraquat is able to moderate the activities of scavenging system enzymes and to influence oxidative stress intensity under drought stress induced by PEG.     

A modified chemiluminescence method for hydrogen peroxide determination in apple fruit tissues

Hydrogen peroxide (H₂O₂) is one of the important by-products produced by plant and fruit tissues during normal metabolism as well as under stress conditions. Evidence suggests that it is actively involved in many physiological activities in plants, including ripening, senescence and the development of disorders. Quantitative measurement of H₂O₂ in fruit has been a challenge due to variations in methodologies, and their sensitivities and interferences present in plant samples. Among the currently used methodologies, chemiluminescence (CL) is one of the most promising, due to its high specificity and sensitivity. However, direct application of CL methods developed for leaf analysis is not suitable for fruit, especially fruit peel tissues, possibly due to interfering compounds in fruit tissues. In this study, evaluation of the efficiency of removal of interfering compounds by PVP, PVPP and activated charcoal revealed that the PVPP is the most effective compound to remove the interference. This modified protocol can measure H₂O₂ content in apple peel and flesh tissues. ‘Red Delicious’ apple peel and flesh tissues were measured with amount of 1.48 and 1.03 μmol/g FW, respectively. The established protocol can also be used for a wide variety of tissues in addition to apple fruit, including strawberry tissues (fruit, calyx and leaves) and spinach leaves. This protocol was applied to determine the H₂O₂ concentration in 1-MCP and DPA treated apples after 5 months of storage, but no significant difference in H₂O₂ in those samples was found. Direct comparison of CL with a commercial hydrogen peroxide measurement OXIS kit was also made. The challenges to accurately assay H₂O₂ in fruit/plant tissue were discussed.     

Impact of controlled atmosphere storage conditions on storability and consumer acceptability of sweet cherries ‘Regina’

Summary

Sweet cherries obtained from a rain-protected orchard were subjected to various controlled atmosphere storage conditions for up to seven weeks. Quality parameters responded differentially to various CA-conditions: changes in fruit firmness, sugar content and colour were mostly not significant. However, the storage conditions exerted significant impact on other parameters such as respiration rate, RQ, ATP- and ADP-concentrations. Air-stored fruits respired at significant higher rates than CA or ultra low oxygen-stored fruits. Moreover, the impact of CA-storage conditions persisted even after a conditioning period of 36 h at room temperature. The ATP and ADP concentrations of sweet cherries behaved similarly, where a combination of reduced O₂ and very high CO₂ concentration (12% or above) resulted in highly reduced ATP-concentration in the fruit tissue. A taste panel considered fruits stored under 6% CO₂ + 2% O₂ as good, although there was a strong indication that it is better to store sweet cherries for a limited time (up to five weeks) under a low O₂ concentration combined with a high CO₂ concentration (12%) or under a high O² concentration combined with a very high CO₂ (18%).     

间歇升温对冷藏桃果实游离脯氨酸含量和冷害的影响

观察分析了间歇升温对冷藏大久保桃果实游离脯氨酸含量、细胞膜透性及冷害的影响,结果表明:冷藏(2±1℃)30d及4d货架期(25—28℃)后,升温24h和36h的桃果实未发生冷害,脯氨酸含量在货架期下降;升温12h和对照的果实冷害严重,脯氨酸含量在货架期急剧上升,显著和极显著高于前两个处理,冷害越严重,值越大。细胞膜透性与冷害发生及严重程度无关,冷藏期间升温处理果实的膜透性大于对照,货架期结束时,各处理间无显著差异。     

Fruit quality and respiration of ‘McIntosh’ apples in response to ethylene,very low oxygen and carbon dioxide storage atmospheres

Storage of ‘McIntosh’ Apples (Malus domestica Borkh.) in a controlled atmosphere (CA) with very low O₂ (1.5% CO₂ + 1.0% O₂, 2.8°C) retained greater fruit firmness and titratable acids during storage and during subsequent air storage than apples stored in conventional CA (5.0% CO₂ + 3.0% O₂, 2.8°C). The rate of firmness loss during subsequent 0°C air storage decreased with length of storage in CA. Storage of apples in very low O₂ for 40 or 80 days decreased the rate of firmness loss in subsequent 0°C air storage as compared to the rate of firmness loss in conventional CA fruit, but the rate of firmness loss in 0°C air storage subsequent to 160 or 320 days of conventional CA was significantly less than the loss in similar fruit stored in very low O₂ atmospheres.A modified atmosphere with 1.0% O₂ decreased the rate of C₂H₄ accumulation in storage, and fruit production of both C₂H₄ and CO₂ after storage opening in comparison with similar fruit in conventional CA. The accumulation of C₂H₄ in storage chambers was increased with increasing O₂ levels, but the rate of increase depended upon the CO₂ level. C₂H₄ storage accumulation was stimulated by the presence of CO₂ at 0.5% O₂, but was suppressed by CO₂ when 3.0% O₂ was maintained.Retention of fruit firmness and titratable acids in apples stored in 1.5% CO₂ + 1.0% O₂ were insensitive to very low (0.231 ml l^?1) or very high (2440 ml l^?1) C₂H₄ levels in storage. Scrubbing C₂H₄ (0.304 ml l^?1) from chambers held at 5.0% CO₂ + 3.0% O₂ resulted in significantly firmer fruit after storage, but this effect was not significant after shelf life of 7 days at 20°C.