Chilling-injury in cucumber fruits. VI. The mechanism of pectin de-methylation

By incubating the homogenate of cucumber fruits in vitro, pectin de-methylation was considerably accelerated especially at near neutral pH. Histo-chemical observations based on detection of SH-protein present in sieve tubes, revealed that the cell walls of the fruits chilled at 0°C for 3 days contained the tube constituents, in which pectinmethylesterase was also found. The esterase of the tubes was cold-labile. All the esterases present in a fruit were activated by an addition of ascorbic acid, a reducing agent.The set of these results, together with our previous papers, suggests that in cucumber fruits chilling may at first break the plasmalemma of sieve tubes, whose exudate outflows into the cell walls of tissue cells. The subsequent contact between the tube esterase and wall pectin results in the pectin de-methylation, which makes elastic cell walls rigid and fragile. This ultimately leads to occurrence of water-stress injury. A decrease of redox potential in the chilled fruits may serve for raising the activity of the cold-labile tube esterase.     

Chilling-injury in cucumber fruits. I. Effects of storage temperature on symptoms and physiological changes

Cucumber fruits transferred to a warm temperature after chilling displayed various symptoms of chilling-injury. In cucumbers chilled to 0°C, vertical fine wrinkles and/or shallow pitting was observed, while after chilling to 5°C deep pitting and/or surface depressions were apparent. Moreover, in the 0°C fruit compared with 5°C fruit, a higher $\text{210}\text{264}$ mμ UV absorption ratio of leakage substances during chilling was observed. These results suggest that the causes of chilling-injury in the 0°C and 5°C fruit are distinct from one another. Weight loss after chilling, the amount of leakage substances, the exudate content from the cut surface of the fruit, redox potential, titratable acidity and respiratory activity were also checked after periods of chilling of 3 to 15 days.     

Chilling-injury in cucumber fruits. II. Chemical analyses of leakage substances and anatomical observation of symptoms

From the chemical composition of leakage substances, it was concluded that there was greater leakage of micro-molecule components in cucumber fruits which had been chilled to 0°C than in fruit chilled to 5°C. However, leakage of macro-molecule components was greater in the 5°C fruit than in the 0°C fruit with longer periods of storage. These results suggest that the plasmalemma develops leakage in the 0°C fruit, whereas there is membrane breakage in the 5°C fruit.Microscopic observations support this assumption.     

Studies on keeping-quality of vegetables and fruits. III. Changes in sugar and organic acid contents accompanying the chilling-injury of eggplant fruits

The mechanism of chiiling-injury in fruits of eggplants (Solanum melongena L. cultivar ‘Hyonaga’) was investigated by determining the sugar and organic acid content during cold storage and after exposure to low temperature for various periods. Fructose, glucose and maltose were detected, and totalled more than 96% of total sugar on the initial day. Total sugar content increased to 30% higher than the initial day after 2 days of cold storage, and after that decreased gradually, while in 20° C-stored fruits it decreased sharply. Fructose, glucose and maltose increased rapidly after transfer from 1° C to 20° C. Succinic, oxalic, malic and citric acid were detected before storage. Malic and citric acid were found to be the main organic acids. The ratio of malic/citric acid in fruits stored at 1°C decreased during storage, while after storage at 20°C it increased. The ratio in fruits after transfer from 1°C to 20°C increased rapidly during the time course. The ratio of malic/citric acid ranged from 6.0 to 6.8 in healthy fruits, while it was below 5.9 or above 7.3 in chilled fruits. It is suggested that according to this ratio the degree of chilling-injury of eggplant fruits might be foreseen.     

Chilling-injury in cucumbers. V. Polysaccharide changes in cell walls

A decline in the hot-water-soluble pectin and an increase in the hot-water-insoluble pectin were observed when cucumber fruits were subjected to chilling temperatures. Infrared absorption spectra revealed the presence of highly esterified carboxyl groups in the soluble pectin, and of free carboxyl groups in the insoluble pectin. An increase of the insoluble pectin during chilling was also found in other chilling-sensitive plants. From these results it is suggested that a de-esterification of pectin and the concomitant increase of polymeric pectin takes place during chilling, making cell walls firmer, and that these pectic changes may be a characteristic common to a number of chilling-sensitive plants.     

Volume and specific gravity of cucumber fruits as affected by moisture condition after harvest

When cucumber fruits were stored at temperatures of 10, 20 and 30°C, in conditions that were so wet that they were able to absorb water freely through the skin, they maintained a constant specific gravity which was a hhigh as it had been at the time of picking, with a hyperbolic increase in volume. After removal to unsaturated vapour conditions at 20°C, their volume and specific gravity changed in a similar way to these of fruit which had not been in wet storage. Storage in humid conditions at 10°C resulted in almost constant specific gravity and volume, but storage at 20 or 30°C produced a gradual increase in volume as well as a decrease in specific gravity of fruits, in spite of the fresh weight showing little change. After removal of these fruits to unsaturated vapour conditions, the volume and specific gravity changed at a much faster rate with their specific rates having a peak. The shorter the humid storage, the higher the peak. The decrease in the specific gravity of picked cucumber fruits was discussed in relation to the presence of water stress.     

Bruising injury of persimmon (Diospyros kaki cv. Fuyu) fruits

This study was performed to monitor the deterioration of bruised persimmon (Diospyros kaki cv. Fuyu) fruits. Freshly harvested fruits were bruised by dropping them from a height of 50 cm onto a steel board and then stored at 0 or 20 °C in temperature controlled chambers for up to 4 weeks. Immediately after the bruising, no visible injury on the fruits was evident, but the fruits deteriorated rapidly during storage. The skin tissues of the fruits stored at 20 °C became more reddish with the duration of the storage, but no such changes were found with the fruits stored at 0 °C. The increase in redness of the skin tissues appeared to be associated with storage temperature, but not with the bruising. The skin tissues also became darker when stored at 20 °C than at 0 °C and this tendency was more obvious with the bruised fruits. Flesh firmness decreased rapidly during storage except for the non-bruised fruits stored at 0 °C. Even the non-bruised fruits rapidly lost their flesh firmness at 20 °C. No significant changes in lipid peroxidation, as expressed by malondialdehyde production, were found between the bruised and the non-bruised fruits during the storage either at 0 °C or at 20 °C. This implies that the fruit deterioration caused by bruising is not due to the consequences of lipid peroxidation. Polyphenol oxidase activity increased more rapidly in the bruised fruits than in the non-bruised fruits during storage. The bruising had more effect on increasing polyphenol oxidase activity than did the storage temperature. Although the increase in polyphenol oxidase activity appeared to be associated with the visual deterioration of the bruised fruits, it did not exactly correspond to the physical deterioration. These results indicate that polyphenol oxidase is not the only factor influencing the deterioration associated with bruising. Cell wall hydrolases are currently being assayed to determine if they also contribute the deterioration following bruising.     

The relation between water stress and the climacteric in respiration of some fruits

Respiration rate, turgor pressure, osmotic pressure and suction pressure were checked periodically after harvest with bananas, pears, apples, tomatoes and cucumbers. There were great differences among species in the courses of osmotic and suction pressure changes, but those of the resulting turgor pressure appeared to be basically similar. Moreover, there was a relatively close relation between respiration rate and turgor pressure.     

Rate of weight loss in proximal and distal halves of picked cucumber fruits as affected by developing seeds

In picked and stored cucumber fruits, the presence of developing seeds increased the proportion of weight loss of the proximal half compared to that of the whole fruit. This difference did not appear after pre-storage separation of the distal half, storage at 5 or 10°C, or in parthenocarpic fruits. This could not be attributed to different rates of transpiration between proximal and distal halves, but must be due to the weight displacement toward the distal region resulting from the movement of water within the fruit. Associated with the redistribution of water, developing seeds induce deteriorating fruit quality through enhancing pithiness of tissue in the proximal part, as reflected by decreasing specific gravity.     

Changes in volume and specific gravity of cucumber fruits after harvest in relation to the recovery from a flaccid appearance

Detached fruits of cucumber (Cucumis sativus L.) developed a flaccid appearance at first, but showed a recovery while stored at a temperature of 12.5°C or above. The recovery occurred in spite of the decline of fresh weight during storage. The higher the storage temperature, the sooner the fruits regained a turgid appearance.After harvesting of cucumber fruits, both their fresh weight and their volume decreased initially, while the specific gravity increased slightly. Accompanying the recovery from a flaccid appearance, however, the specific gravity of the fruits decreased and the rate of decrease in volume was retarded until eventually the fruits began to swell. The increase in volume occurred at any part of a fruit, although in a slightly different manner at the distal quarter.Fruits held at a temperature of 10°C and below, however, remained in a flaccid state during storage. In this case, fruit volume as well as fruit weight continued to decrease, but specific gravity increased gradually.Developed seeds with ivory colored seed coats were found in fruits at the end of storage at 15.0° or 17.5°C, but not in those stored at 12.5° or 10.0°C.     

落叶果树的钙素营养

钙素营养在果树体内有重要的生理作用,且有单向运输的特性.果树缺钙,果实极易发生生理病害.土壤交换性钙缺乏的临界值为400mg/kg土,不同树种的叶片、果实中钙含量的适宜值不同,缺钙的原因很多,但一般可通过土壤施钙、叶面喷钙及果实采后浸钙来矫正.     

番茄裂果的产生与防治

裂果是近年来番茄生产中普遍存在的问题。给生产带来很大损失，影响贮运与运输。裂果后带来的污染和病害感染这些副作用更为严重。特别是东北盛果期正值雨季，防止裂果十分重要。本系统地论述了裂果产生的原因与防治方法。旨在为今后培育抗裂品种提供理论依据。     

桃果实采后生理生化及冷害研究进展

桃果实采后极易发生腐败变质现象,低温可延长果实的贮藏保鲜期,但长期的不适低温冷藏易使果实产生木质化、絮败、果肉褐变、果肉变红、糖酸比失调、固有芳香成分丧失或有害挥发性物质生成等品质劣变症状。不同类型桃果实甚至不同品种桃果实的采后品质劣变规律不同,低温的敏感度及冷害的发生时间点、综合表现特征亦有较大差异,其保鲜技术一直是国际上的难题。笔者对果实品质劣变发生的症状进行归纳,并从酶学、分子生物学和蛋白质组学等方面进行了相关机制阐释。建议对不同肉质类型桃采后生理特性和贮运特性进行系统性研究,制定相应的采后品质劣变调控技术,开发高效、安全的保鲜技术并应用于实践,为桃果实采后处理及保鲜贮运技术的应用提供一定的理论支撑。     

第十届中国果菜产业论坛暨优质农产品产销对接会

邀您共聚中国-广州11月29日-12月2日中国果菜产业发展论坛已连续成功举办了九届,其中前三届分别在北京人民大会堂、国务院招待所、中国科技会堂举行。姜春云、布赫、经叔平等多位前国家领导人出席大会为论坛剪彩揭幕,给予了莫大的支持。论坛赢得了社会的广泛认可,为推动中国果菜产业的可持续发展做出了积极的贡献,已成为推动果菜产业发展最具权威性的平台,并成为一年一度的行业盛会。     

第十届中国果菜产业论坛暨优质农产品产销对接会

邀您共聚[中国-广州]11月29日-12月2日中国果菜产业发展论坛已连续成功举办了九届,其中前三届分别在北京人民大会堂、国务院招待所、中国科技会堂举行。姜春云、布赫、经叔平等多位前国家领导人出席大会为论坛剪彩揭幕,给予了莫大的支持。论坛赢得了社会的广泛认可,为推动中国果菜产业的可持续发展做出了积极的贡献,已成为推动果菜产业发展最具权威性的平台,并成为一年一度的行业盛会。     

Effect of parthenocarpy,peeling and fruit age on the changes in volume and specific gravity of cucumber fruits during storage at 20°C

Either parthenocarpically grown, peeled or at any stage of picking, cucumber fruits showed a tendency to increase in volume and decrease in specific gravity while they were stored under unsaturated vapour pressure at 20°C. The amount of change varied according to the treatment.Recovery from a flaccid appearance occurred in all fruit except very young ones. In those fruits the incipient recovery from wilting, an increase in volume and a decrease in specific gravity, coincided.Parthenocarpic fruits showed an increase in volume at almost the same rate in any transverse quarter of a fruit, in contrast to the pollinated ones in which the most distal quarter enlarged more than the other parts. Pithy appearance of the fruit wall was evenly distributed through a parthenocarpic fruit to a moderate degree, but at the proximal half of a pollinated one it was severe.     

The relationship between nitric oxide and gastric mucosal injury induced by reserpine in rats

AIM: To study the relationship between nitric oxide (NO) and gastric mucosal injury induced by reserpine in rats. METHODS: Sixteen healthy male Wistar rats were randomly divided into control group and experimental group (n=8). NO contents and malondialdehyde(MDA) contents in plasma, gastric mucosa of the rats were respectively determined with Cadmium-reduct plus Greiss and TBA; nitric oxide synthase in gastric walls of the rats were observed using NADPH-diaphorase histochemistry and quantitatively measured with image analyzer. RESULTS: The NO contents in both plasma and gastric mucosa of experimental group were significantly lower than that in control group (P＜0.01),but their MDA contents were both higher than that in control group(P＜0.05,P＜0.01);the densities and A values of nitric oxide synthase (NOS)-positive nerve-cells and nerve fibers in gastric walls of experimental group were all obviously lower than that in control group (P＜0.05,P＜0.01). CONCLUSION: The mechanism of the reserpine-induced gastric mucosal injury in rats might be related to NO insufficiency arisen from the inhibition of NOS activity in NANC nerves in gastric wall,which might weaken the protection to gastric mucosa.     

优质无公害果品生产关键技术

无公害果品是指梨树的生长环境，生长过程以及包装、贮存，运输中未被有害物质污染，或虽有轻微污染，但符合国家标准的果品。无公害果品生产是有其严格标准和程序的，它主要包括环境质量标准，生产技术标准和产品质量检验标准。现将其生产关键技术阐述如下。     

温室黄瓜常见生理性病害的发生及防治技术

经调查发现，近年来棚室黄瓜的生理病害逐年增多，如尖嘴瓜、苦味瓜、生理性萎蔫病、低温生理性病害、叶烧病等，广大菜农在栽培过程中对此十分头痛，这严重影响了黄瓜的产量与品质，因此，及时识别与防治黄瓜生理性病害非常必要。