Genetical and Cytological Aspects of Incompatibility and Sterility in Cultivated Fruits.

Summary

Effects of auxin and gibberellin on changes in pectin polysaccharides and activities of the enzymes, pectin methylesterase and polygalacturonase were assayed in fruits of cape-gooseberry (Physalis peruviana L. ‘Rashbhori’) during their development and ripening. The water-soluble pectic fractions accumulation more in the auxin-treated fruits than in the control, while gibberellin raised the level of the acid-soluble and alkali-soluble fractions. Treatments with auxin increased polygalacturonase activity and gibberellin proved to be highly effective in reducing its activity. The significance of these findings in relation to pectin solubilization is discussed.     

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.     

Leatheriness and mealiness of peaches in relation to fruit maturity and storage temperature

Summary

`Huangjin' peaches (Prunus persica Batsch) were harvested at commercial harvest time (commercial) and 20 d before (early) or after (later) commercial harvest. Fruit from each harvest were stored at three temperature regimes (0, 5 and 10°C) at 95% r.h. After four weeks of storage at 0 or 5°C, early harvested fruit developed more leatheriness but less mealiness and later harvested fruit did not develop leatheriness but developed more mealiness comparedwith fruit from commercial harvest. Overall, fruit stored at 5°C developed more mealiness but less leatheriness than fruitat 0°C for the same period of storage. When stored at 10°C for two weeks, after which fruit were senescent, fruit did not develop any leatheriness or mealiness regardless of harvest times. Fruit with leatheriness were firmer (>30 N) thanjuicy or mealy fruit (<10 N) after the same period of cold storage and 4 d at 20°C. Mealy fruit were as soft as juicy fruit. 1-Aminocyclopropane-1-carboxylate oxidase (ACO) activity, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and polygalacturonase (PG) and galactosidase (GAL) activities were lower, and insoluble pectin content was higher in leathery fruit than that in juicy or mealy fruit. ACO, PG and GAL activity, ACC, and insoluble pectin content were similar between mealy and juicy fruit.     

Fractional changes of pectic polysaccharides in different tissue zones of developing guava (Psidium guajava L.) fruits

Cell-wall pectic polysaccharides were fractionated by sequential extraction with water, 1% potassium oxalate at room temperature, 0.05 M HCl at 100 °C and 0.05 M NaOH at 4 °C from the three specific tissue zones, i.e., outer pericarp (OP), middle pericarp (MP) and inner pericarp (IP) of the guava fruits during their development and ripening. The water and oxalate-soluble pectic fractions were found to increase, while acid and alkali-soluble pectic fractions had a decreasing trend at ripening phase of fruit, irrespective of the different tissue zones. However, the extent of pectic solubilization was more pronounced in IP region as compared to OP and MP zone of the fruit tissue. The differential degradation of pectic polymers thus points out that ripening as well as tissue softening of guava fruits are centrifugally expressed as evidenced by higher accumulation of sugar and soluble pectic polysaccharides in IP zone of the fruits.     

Differential propylene induced ethylene production in ‘Anjou’ pears during storage at chilling and non-chilling temperatures

Summary

‘Anjou’ pears were harvested from the Mid-Columbia Experiment Station, Hood River, Oregon, at 67 N firmness, stored at –1° or 20°C for 85 d and periodically tested for sensitivity to 0 or 500 µl l^?1 propylene for at least 14 d at 20°C. Climacteric ethylene of pears stored at 20°C remained at low levels and started rising on the 90th day. Pears chilled at –1°C required 70 d to ripen and produced climacteric ethylene immediately upon transfer to 20°C. The sensitivity of the fruit to exogenous propylene increased progressively with storage time at –1°C. However, the non-chilled fruit responded to propylene similarly to freshly harvested fruit during the first 55 d of storage, then similarly to –1°C-stored fruit up to 85 d. Anjou pear ripening events and the sensitivity of the fruit to exogenous propylene developed differently in storage at non-chilling temperature compared with chilling temperature.     

Involvement of 1-methylcyclopropene in ripening of harvested mei (Prunus mume) fruit

Summary

Harvested mei (Prunus mume) fruit were stored at 20°C after exposure to 500 nl l^–1 1-methylcyclopropene (1-MCP) for 8 h. Firmness, peel colour, chlorophyll content, chlorophyllase activity, soluble solids content (SSC), titratable acidity (TA), respiration and ethylene production, and cell wall hydrolysis enzyme activities were monitored to determine the efficacy of 1-MCP treatment in delaying mei fruit ripening compared to untreated control fruit. Results showed that control ‘daqinghe’ mei fruit displayed typical climacteric patterns of respiration and ethylene production. Peak CO₂ production and ethylene production were observed after 6 d. Fruit softening was accompanied by a progressive decrease in colour parameters expressed as hue angle (h°), chlorophyll content, SSC, TA and increases in chlorophyllase, pectin methylesterase (PME) and polygalacturonase (PG) activities. 1-MCP treatment prior to the climacteric increase significantly delayed the onset of the climacteric peaks of CO₂ and ethylene production. These delays were associated with reductions in fruit softening, consistent with delaying the activities of PME and PG. Fruit treated with 1-MCP exhibited less peel colour change from green-to-yellow because of their lower levels of chlorophyllase activity and less chlorophyll breakdown. Moreover, 1-MCP treatment also significantly retarded reductions in SSC and TA compared with control fruit. The shelf-life of mei fruit ripening was increased by 4 d following 1-MCP treatment. Thus, 1-MCP treatment can markedly extend the post-harvest life of ‘daqinghe’ mei fruit.     

Physiological changes in boysenberry fruit during growth and ripening

Summary

Boysenberries (Rubus hybrid) were harvested at five developmental stages (green, “turning”, pink, red and purple) to study changes associated with flavour, colour and firmness, with a particular focus on the different enzymes involved in chlorophyll degradation or cell wall degradation. The level of reducing and non-reducing sugars increased 109- and 52-fold, respectively, between the “turning” and the purple stage. Titratable acidity increased by 84% between the green and the pink stage, but dropped by 41% between the red stage and full ripening. Total phenols displayed their highest values in green and “turning” fruit. Chlorophyll a and b degradation occurred mainly during the early stages of development, and was paralleled by a 2.3-fold increase in chlorophyllase activity and a 5-fold increase in Mg-dechelatase activity between the green and the red stages. Chlorophyll peroxidase activity was high at the green stage, but did not change significantly after the “turning” stage. This is the first report on the activity of chlorophyll-degrading enzymes in Rubus spp. fruits. Anthocyanins increased 11-fold between the “turning” and the pink stages, and an additional eight-fold between the pink and the purple stages. Fruit firmness decreased noticeably during ripening, with a concomitant 10.75-fold increase in polygalacturonase activity, beginning at the “turning” stage. Endo- -1,4-glucanase and -galactosidase activities rose 9.2- and 6.7-fold, respectively, after the pink stage and paralleled the major softening process taking place between the pink and purple stages, when fruit firmness decreased from 3.83 N to 0.29 N. Pectin methylesterase activity was high in pink and red fruit, but decreased by 21% as the fruit turned from red to purple. This is the first report on cell wall enzyme activities whose combined action might be required for the breakdown of natural cell wall substrates during ripening in boysenberry, as happens in other soft fruits.     

Effect of calcium supply on the physiology of fruit tissue in ‘Andesu’ netted melon

Summary

Fruit development and physiological traits were evaluated in ‘Andesu’ netted melon plants grown with and without calcium. Calcium exclusion accelerated softening, alcoholic fermentation and ethylene evolution of fruit compared with those supplied with calcium, but the opposite trend occurred with sucrose accumulation. A significant difference of calcium concentrations in the fruit between treatments was observed at the developing stage of the fruit (P<0.05), but the difference became smaller as fruit matured. In the mesocarp tissue from the basal hemisphere, calcium concentrations in the NaCl soluble fraction at ripe fruit stage differed significantly (P<0.05) between calcium treatments but no significant difference was detected in the inner mesocarp of the distal hemisphere. Calcium exclusion did not lead to the development of water-soaked symptoms in the mesocarp tissue of ripe fruit. Uronic acid concentrations in ionically bound pectin fraction did not differ between calcium treatments throughout fruit development. In covalently-bound pectin fraction, however, uronic acid concentration of ripe fruit was significantly lower in calcium-excluded plants than in calcium-supplied plants (P<0.05). Our results suggest that: first, accelerated fruit softening under calcium deficient conditions might result from promoted ethylene evolution rather than from the shortage of ionically-bound calcium in cell walls, second, calcium deficient condition does not necessarily lead to water-soaked symptoms in tissue of ‘Andesu’ melon fruit.     

‘黄冠’梨采后热处理和钙处理对其钙形态及细胞壁物质代谢的影响

 以‘黄冠’梨为材料,研究了采后热处理（38 ℃热空气24 h）,钙处理（6% CaCl₂浸果15 min）及热加钙处理（6% CaCl₂ + 38 ℃）对果实低温贮藏过程中钙形态及细胞壁物质代谢的影响,以清水浸果为对照。结果表明：果胶钙为果实中主要的钙形态,其含量占全钙的49.7% ~ 55.8%,钙处理、热加钙处理果实的总钙含量与对照相比分别增加了22.95和31.58 µg · g^-1;钙处理、热加钙处理显著抑制了果实纤维素、原果胶、水溶性钙及果胶钙含量的下降,促进了草酸钙含量的增加,延缓了果实硬度的下降;热处理、热加钙处理显著降低了多聚半乳糖醛酸酶（PG）、果胶甲酯酶（PME）和纤维素酶活性。相关分析表明,果实硬度与纤维素、原果胶、水溶性钙和果胶钙含量呈极显著正相关,与可溶性果胶含量呈极显著负相关;PG和纤维素酶与果实硬度均呈极显著负相关,PME与果实硬度的相关性不显著。钙处理、热加钙处理通过抑制可溶性钙向难溶性钙转化、细胞壁组成成分降解以及降低细胞壁降解酶活性,延缓果实软化,其中以6% CaCl₂ + 38 ℃的处理效果最好。     

猕猴桃衰老过程中PG,果胶质和细胞壁超微结构的变化

采后美味猕猴桃秦美果肉组织乙烯生成不断增加的同时，ＰＧ９多聚半乳糖醛酸酶）活性迅速提高，致使原果胶大量降解为可溶性果胶，细胞结构受损，胞壁纤维松弛、细胞器逐步空泡化，果肉由硬变软。ＰＧ活性和果肉硬度的变化呈明显的负相关。     

Changes in cell wall polysaccharides and cell wall degrading enzymes during ripening of Fragaria chiloensis and Fragaria ×ananassa fruits

Chilean strawberry (Fragaria chiloensis) is arising as a new fruit crop that can diversify the world supply of berries. Fruit softening is thought to be linked to an extensive modification of pectin and hemicellulosic cell wall fractions which in turn is determined to a great extent by the action of some cell wall-modifying enzymes. The objective of this work was to compare cell wall changes and the enzyme activities of pectin methylesterase (PME), polygalacturonase (PG), endoglucanase (EGase), α-arabinofuranosidase (AFase), β-galactosidase (βGal), and β-xylosidase (βXyl) between F. chiloensis and Fragaria ×ananassa (cv. Chandler) at three fruit developmental stages: large green (LG), turning (T) and ripe (R). A rapid decrease in fruit firmness between LG and T stages was observed in both species; nevertheless firmness reduction in F. chiloensis was steeper than in F. ×ananassa. This could be related to a faster loss of HCl-soluble polymers (HSP fraction) presented in F. chiloensis fruit. However, commercial F. ×ananassa showed a greater depolymerization of HSP polymers than F. chiloensis. With the exception of PME, the activity of all assayed enzymes was higher in F. chiloensis than in F. ×ananassa fruits. The role of PG and EGase seems to be central in both species: these enzymes are correlated to the decrease in the content of HSP and NaOH-soluble polymers (NSP fraction), respectively. In addition, activity levels of βGal and βXyl were significantly correlated with fruit firmness reduction in F. chiloensis and F. ×ananassa, respectively.     

Physiological changes during development and ripening of ‘Perlita’ muskmelon fruits

‘Perlita’ muskmelon fruit (Cucumis melo L.) grown under both field and greenhouse conditions were sampled at 10-day intervals for 50 days after pollination to determine changes in pH, soluble sugars, total protein, β-carotene, tissue firmness, cell wall composition, cell wall degrading enzymes, total calcium and bound calcium. The sucrose content of fruits increased substantially after 40 days post-anthesis, which compensated for the significant decreases in glucose and fructose content. Acidity and total protein remained relatively unchanged throughout the sampling period. β-carotene increased from 0.3% (w/w) at 10 days post-pollination to 2.7% (w/w) in 50-day old melons. Tissue firmness measured by shear force decreased by 400% between 30 and 50 days postanthesis. No significant changes in cellulose, hemicellulose and pectin content of the cell wall were detected. Cx-cellulase and pectinmethylesterase activity were detected but remained constant or declined during ripening; polygalacturonase activity was not detected. The major compositional changes in developing and ripening fruit were sucrose, glucose, fructose and β-carotene. In spite of dramatic decreases in tissue firmness, concomitant changes in crude cell wall fractions and associated cell wall degrading enzymes were not detected.     

The effect of temperature on certain chemical changes and the storage behaviour of jujube fruits (Zizyphus spinachristi (L.), Willd.)

Summary

Jujube fruits (Zizyphus spinachristi (L.) Willd.) cv. Bambawi were harvested at the mature green stage and stored at 10°C and 27–30°C. Titratable acidity and total chlorophyll decreased as the fruit matured, the rate of decline being more rapid at the higher temperature. Total soluble solids, carotenoids and ascorbic acid contents of the fruit increased towards maturity, the increase being faster at the higher temperature. Jujube fruits could be stored for six days at room temperature and twenty-five days under refrigeration at 10°C.     

Influence of 1-methylcyclopropene on pectic enzyme activities,gene expression,and cell wall modification in papaya (Carica papaya cv. ‘Sunrise’) fruit

SUMMARY

‘Sunrise’ papaya fruit harvested at two stages of maturity [colour break (< 10% yellow peel colour) and 25% yellow peel colour] were treated with 100 nl l^–1 1-methylcyclopropene (1-MCP) to determine its effects on ripening, on the activities and levels of gene expression of polygalacturonase (PG), pectin methyl esterase (PME), and βgalactosidase ( βGal), and on the degradation of cell wall components. 1-MCP delayed ripening and the onset of the climacteric, although the peak in the respiration rate was almost the same as that in untreated control fruit. Colour-break fruit treated with 1-MCP exhibited a continuous increase in ethylene production, but at a lower rate than in control fruit. Consequently, 1-MCP-treated fruit ripened with a concomitant reduction in firmness, which was accompanied by an increase in PG and βGal enzyme activities and gene expression. On the other hand, fruit treated with 1-MCP at the 25% yellow stage exhibited lower levels of ethylene production and developed pulp with a rubbery texture at the ripe stage which was attributed to reduced PG, βGal, and PME enzyme activities and gene expression. This was consistent with the higher level of cell wall polysaccharides measured in 1-MCP-treated fruit. The above results indicated that ‘Sunrise’ papaya fruit can be treated with 1-MCP at the colour break stage since they have a greater capacity to recover from the effects of 1-MCP than fruit treated at the 25% yellow stage.     

不同发育时期的荔枝花芽冷敏感性比较

【目的】为了探明不同发育时期的荔枝(Litchi chinensis Sonn.)花芽的冷敏感性差异,【方法】以发生在2008年1月下旬至2月下旬的极端低温作为低温处理的条件,研究了低温对‘妃子笑’与‘糯米糍’2个品种的"白点"(一级侧花序原基)和初生花序(花序轴伸长的一级侧花序,长1~2 cm)2种不同发育时期的花芽相对电导率、过氧化氢(H2O2)含量、花芽表面茸毛以及细胞超微结构的影响。【结果】结果表明,低温使花芽的H2O2含量升高,相对电导率增大,无论是低温期间还是温度回升后,‘妃子笑’"白点"的相对电导率低而且变化幅度小。受冷害的初生花序的茸毛较杂乱,表面有裂痕和碎片,但‘糯米糍’的裂痕和碎片相对较多。受冷害的"白点"茸毛排列较初生花序有序,表面也有裂痕,但‘糯米糍’的"白点"表面裂痕较多。而未受冷害的花芽茸毛致密而有条理,没有裂痕。2个品种受害细胞的细胞壁变得模糊,液泡膜出现破损,细胞质渗漏到液泡中,而没有受害的初生花序或"白点"上的细胞壁、液泡膜清晰。【结论】研究结果显示花序比"白点"对低温更敏感。     

Comparative studies on the postharvest physiology of fruit from different species of Annona (custard apple)

Summary

Fruit of three Annona species, viz. cherimoya (A. cherimola Mill), sugar apple (A. squamosa L.) and custard apple (atemoya, Annona X) were ripened in ethylene-free air and under propylene. Differences were found in patterns of respiration, ethylene production and fruit firmness changes during ripening. Cherimoya and custard apple fruits showed two successive rises in respiration rate whereas sugar apple fruits showed only one. Ethylene production showed one main peak but the onset of rapid ethylene production occurred after the beginning of the respiration climacteric in all three species. Custard apple fruit had acceptable eating quality (as judged by sensory assessments and chemical analyses of pulp) for up to four days after first detectable softening, when ripened at 20°C in ethylene-free air or under propylene. Fruit ripened in ethylene-free air had better ripe fruit quality than fruit ripened under propylene.     

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.     

Physical and Chemical Characterization of Dovyalis Fruits

Abstract

The objective of this work was to establish physical and chemical characterizations of dovyalis hybrid fruits (Dovyalis abyssinica and D. hebecarpa). Samples of 25 fruits were characterized by evaluation of length and width, weight, percentage and number of seeds per fruit, peel percentage, pulp percentage, total soluble solids (TSS), titratable acidity (TA), vitamin C and TSS/TA ratio. Dovyalis fruit has good physical quality for market with an average of 75% pulp. Vitamin C content averaged 120.3 mg/100 g of fresh fruit, characterizing dovyalis as a good source of vitamin C.     

Effect of storage temperature on ripening and quality of custard apple (Annona squamosa L.) fruits

Summary

The effect of storage temperature on ripening, shelf life and chemical composition of custard apple (Annona squamosa L.) fruits stored at 10,15,20 and 25°C was studied. The safe range of storage temperature was found to be between 15 and 20°C, with maximum shelf life at 15°C. The ripening of fruits was observed on days 4, 6 and 9 of storage at 25,20, and 15°C respectively. The colour of the pulp, texture, taste and flavour of ripe fruits held at 25 and 20°C were superior followed by fruits stored at 15°C. At 10°C, the fruits became hard with surface blackening, messy pulp and less sweetness. The major changes during ripening were a continuous decrease in fruit firmness and starch content and a continuous increase in TSS and sugars, the changes being more rapid at 25 and 20°C than at 15 and 10°C. The acidity and ascorbic acid contents increased slightly during the initial stages of ripening followed by a decline, in the fruits stored at different temperatures. Custard apple fruits stored at 25 and 20^CC had a clear climacteric peak whereas those stored at 15 and 10°C did not show any distinct rise in respiration rate. Ethylene peak (2.40 µl kg^–1 h^–1) coincided with the respiratory climacteric at 25^CC storage, corresponding with the peaks in TSS, sugars, ascorbic acid and acidity.     

Fruit-Thinning Effects on the Development and Storage Quality of Cox’s Orange Pippin Apple Fruits

Fruit-thinning treatments were applied in the three seasons 1963–65 to Cox trees to investigate the relationships between leaf : fruit ratio, fruit size, cell volume and cell number, and the incidence of rotting and disorders following air storage at 2·8° C. (37° F.) and o° C. (32° F.). Progressively more severe thinning was required, sis fruit development proceeded, to obtain a similar increase in fruit size. This declining response to thinning was accompanied by a progressively smaller increase in the cell numbers of fruits as the treatments were delayed. Thinning also caused an increase in cell-enlargement rate but the magnitude of the response varied between different experiments and did not appear to be related to the developmental stage at which the treatment was applied.

The larger fruits from thinned trees were more susceptible to bitter pit, breakdown, and rotting caused by Gloeosporium perennans, but were less susceptible to low-temperature injury than fruits from unthinned trees. Bitter-pit incidence was related to fruit size within each treatment and was more severe in fruit where the ratio between the potassium and calcium concentrations was high. Low-temperature injury was associated with fruit with low dry matter and potassium contents. Susceptibility to this disorder and to rotting was also influenced by fruit maturity as measured by the progress of the climacteric rise in respiration rate. There were no marked relationships between storage disorders and the numbers or size of cells in fruits produced by the various treatments included in these experiments.