Effect of Water Stress on Ethylene Production by Detached Leaves of Valencia Orange (Citrus sinensis Osbeck)

Detached leaves of Valencia oranges, Citrus sinensis Osbeck, emanated ethylene at markedly higher rates and contained more endogenous ethylene when placed under water stress at 55% relative humidity than when placed in water-saturated air. Water stress induced defoliation from detached branches. Relieving the water stress of such leaves by transfer to a mist chamber resulted in lowering of the rates of ethylene emanation to the level occurring in leaves maintained continuously in a mist chamber. This ability to recover from the water stress was evident for only up to 10 to 20 hours of stress, when the relative turgidity of the leaves was 50 to 60%. Beyond that time the level of ethylene emanation of stressed leaves was not lowered by rehydration in a mist chamber; these overstressed leaves could not reabsorb their original water content. Ethylene emanation was in high correlation with the relative turgidity of detached leaves of oranges.     

Involvement of endogenous ethylene in the induction of color change in shamouti oranges

Reducing the level of endogenous ethylene in detached Shamouti oranges (Citrus sinensis L. Osbeck) by means of subatmospheric pressure did not alter the rate of chlorophyll destruction and color changes during the first 8 days after harvest in the presence or absence of exogenous ethylene. Reducing the activity of ethylene by means of CO₂-known to be a competitive inhibitor for ethylene-inhibited chlorophyll destruction and color change in Shamouti oranges ventilated with ethylene, but had no effect on these processes in the absence of applied ethylene. The evidence presented indicates that endogenous ethylene may not be the primary inducer for the natural color change in detached Shamouti oranges.     

INFLORESCENCE TYPES AND FRUITING PATTERNS IN HAMLIN AND VALENCIA ORANGES AND MARSH GRAPEFRUIT

The structural, flowering, and fruit-setting patterns of inflorescences of mature Hamlin and Valencia orange and Marsh grapefruit trees were studied for three years. Several development patterns were found, some of which were relatively consistent for the different varieties or years of study. The sequence of anthesis on an inflorescence was: apical flower first, then basal flower, then the subapical flower. Terminals on which the earlier flowers appeared tended to have more inflorescences than those on which flowers appeared later. Inflorescences on which earlier flowers appeared also produced more flowers than those which began flowering later. Inflorescences that began flowering later were more likely to have leaves or have a greater number of leaves than earlier inflorescences. More than half of the inflorescences carried no leaves, and most of these had one flower. No evidence of a relationship between number of flowers and length of the inflorescence was found. Fruit set occurred primarily during the latter part of the flowering period. Many fruit were set on inflorescences without leaves, but on the basis of percent of flowers setting fruit, inflorescences with leaves were more productive. The greatest fruit set occurred in the subapical position on the inflorescence. With growth changes these fruit often appeared to be developing in the apical position. These patterns generally differed little from year to year. Variations may have been due to the differences in the number of flowers produced by the trees. Results were also similar between Hamlin and Valencia oranges. Patterns on Marsh grapefruit resembled those for the oranges but were frequently less consistent.     

In vitro growth and ripening of strawberry fruit in the presence of ACC, STS or propylene

Strawberry ( Fragaria ananassa Duch.) fruit exhibit limited capacity for continued development following harvest. This problem can be circumvented by maintaining harvested strawberry fruit in solutions containing sucrose and a bactericide. In this study, we investigated the respiratory and ethylene production kinetics and ethylene responsiveness in strawberry fruit harvested immature and ripened in vitro in the presence of propylene. The effects of 1-amino-cyclopropane-1-carboxylic acid (ACC) and silver thiosulfate (STS) alone and in combination were also examined. Respiration and ethylene patterns of fruit harvested green and developed in vitro declined with maturation and ripening, as did those of field-grown fruit harvested at different stages of ripeness. Exposure of detached green strawberry fruit to 5000 μl litre^-1 propylene failed to stimulate respiration or ethylene production, but advanced pigmentation changes and fresh-weight gain significantly. Excised fruit provided with 1 mol^-3 ACC exhibited increased ethylene production, enhanced fresh-weight gain, and accelerated anthocyanin accumulation, but showed no change in respiration. The developmental response of harvested strawberry fruit to propylene or ACC was dependent on fruit maturity at harvest, with white fruit exhibiting greater insensitivity compared with green fruit. Silver thiosulfate (0.5 mol^-3) applied alone or in combination with ACC failed to delay ripening in excised strawberry fruit. These experiments demonstrate that ripening in detached strawberry fruit can be modified by ethylene only in green fruit that are provided with a carbohydrate source. Ethylene, when applied exogenously as ACC or propylene to green fruit, can slightly increase fruit growth and the rate of colour development.     

The Role of Ethylene in the Shedding of Red Raspberry Fruit

The production of ethylene by red raspberry (Rubus idaeus L.cv. Glen Clova) fruit increased climacterically during development.The concentration of ethylene within green fruit was low butincreased substantially as fruit abscission and ripening commenced.The receptacle contained higher concentrations than the drupeletsat all stages measured. In the mature ripening fruit the ethyleneconcentrations were found to be physiologically significant,and would accelerate the abscission of large green non-abscisingfruit if supplied as a fumigant. The addition of ethylene toripe fruit did not accelerate abscission, probably because saturatinglevels occurred naturally within these fruit. Reduction of ethylenesynthesis rates using the inhibitor of ethylene production aminoethoxyvinylglycine(AVG) reduced the rate of abscission zone weakening which occursin detached large green fruit. The rate of ethylene productionwas found to be dependent on the supply of the precursor l-aminocyclopropane-l-carboxylicacid (ACC). This only accumulated to any extent in those ripefruit with high rates of ethylene production. Rubus idaeus, raspberry, abscission, fruit ripening, ethylene, aminocyclopropane-l-carboxylic acid     

Characterization of allotetraploids derived from protoplast fusion between navel orange and kumquat

In this study, we aimed to produce a citrus fruit with no seed and with edible peel. Therefore, the seedless Yoshida navel oranges (Citrus sinensis ‘Yoshida navel’) and Jangsil kumquat (Fortunella japonica) with edible peel were used as the starting materials. Since two varieties of different genera and different flowering periods would be difficult to crossbreed, protoplast fusion was conducted using the polyethylene glycol method. Yoshida navel orange and Jangsil kumquat were used as an embryogenic callus line and a mesophyll line, respectively. The regenerated plants were analyzed by flow cytometry to identify tetraploids, which were further evaluated by polymerase chain reaction, using simple sequence repeat markers specific for the nuclear and cytoplasmic organellar DNAs of the two parents, to confirm allotetraploids and cybrids. Sixteen allotetraploids were finally produced and characterized phenotypically for leaf morphology and fruit quality. All allotetraploids contained mitochondria originating from Yoshida navel orange; 12 contained chloroplasts derived from navel orange whereas four contained chloroplasts of kumquat origin. We investigated both plant and fruit characteristics of allotetraploids derived from the protoplast fusion of navel orange and kumquat. The sizes of the allotetraploid leaves were intermediate between those of both parents. However, in contrast to the spindle-shaped leaves of both parents, those of the allotetraploids were obovate. Petiole wings were absent in the allotetraploids, a known kumquat trait. Similar to navel oranges, flowering time was mid-May, and pollen was sterile, whereas fruit size, external shape, soluble solids content, and acidity were all intermediate between the two parents. Peel thickness and the number of segments were similar to those of kumquat, and flesh weight was similar to that of navel orange. Collectively, these results indicated that the intergeneric allotetraploids derived from navel orange and kumquat inherited favorable traits of both parents and could be produced and selected despite a lack of extensive parental variation. This is one of the first reports showing fruiting results of protoplast-fused citrus plants. The study reported characteristics of the fruits from both the original plants as well as from the protoplast-fused plant. Detailed characteristics of the allotetraploid fruit produced by protoplast fusion would be very helpful for future polyploid studies.

     

Use of lysophosphatidylethanolamine, a natural lipid, to retard tomato leaf and fruit senescence

We studied the influence of lysophosphatidylethanolamine (LPE) on the pattern and rate of ethylene production and respiration of tomato ( Lycopersicon esculentum cv. H7155) leaflets and fruit. Leaflets that had been senescing on the plant showed a climacteric-like rise in ethylene production but not in respiration rate which decreased continuously with leaf age. Detached leaflets had a climacteric-like pattern in respiration whether they were incubated in complete darkness or in light. Detached leaflets incubated in the dark had higher rates of ethylene production and CO₂ evolution than did light-incubated leaves. There was no change in the pattern of ethylene production or CO₂ evolution as a result of LPE treatment. However, LPE-treated attached and detached leaflets had consistently lower rates of CO₂ evolution. The reduction in CO₂ evolution by LPE was most pronounced at the climacteric-like peak of the detached leaves. LPE-treated leaflets had a higher chlorophyll content and fresh weight and lower electrolyte leakage than the control. LPE-treated fruits had lower rates of ethylene and CO₂ production than did the control. LPE-treated fruits also had higher pericarp firmness and lower electrolyte leakage than the control. The results of the present study provide evidence that LPE is able to retard senescence of attached leaves and detached leaves and tomato fruits. Several recent studies suggest that lysolipids can act in a specific manner as metabolic regulators. Our results suggest a specific role of lysolipid LPE in aging and senescence     

Cellulase Activity, Endogenous Abscisic Acid, and Ethylene in Four Citrus Cultivars during Maturation

At maturity, the fruit of two early maturing orange cultivars, Hamlin and Pineapple (Citrus sinensis [L.] Osbeck), contained more ethylene and abscisic acid than the late maturing Valencia and Lamb Summer (C. sinensis [L.] Osbeck) cultivars. Ethylene (up to 95 nl/l in internal atmosphere) and abscisic (50 μg/kg dry weight flavedo) increased most rapidly in Pineapple, leading to increased cellulase activity and loosening of the fruit. Fruit of the two late maturing cultivars contained less than 25 nl/1 ethylene and 40 μg abscisic acid/kg dry weight of flavedo at peak maturity. Cellulase activity and loosening of the fruit of these late maturing cultivars was slight.     

Water-deficit Stress, Ethylene Production, and Ripening in Avocado Fruits

Differential rates of water loss were achieved in picked avocado (Persea americana Mill.) fruits, either by controlling the evaporation rate or by supplying water through the fruit stalk. A negative linear correlation was found between the daily rate of water loss from fruits and their ripening, as determined by the time from harvest to peak of ethylene production. Ripening rate was hastened by 40% in fruits which had lost water at rate of 2.9% fresh weight per day, compared with those which lost only 0.5% per day.     

Growth and maintenance respiratory costs of cucumber fruits as affected by temperature, and ontogeny and size of the fruits

The rates of dry weight increase and respiration of fruits were measured throughout fruit ontogeny at 20, 25 and 30°C in cucumber ( Cucumis sativus L. cv. Corona). By maintaining one or five fruits per plant, which strongly affected fruit dry weight but not ontogeny, the effects of fruit size and ontogeny on respiration could be studied separately. The respiration rate per fruit followed a sigmoid curve during fruit ontogeny, while the specific respiration rate (respiration rate per unit dry weight) declined with time after anthesis. The specific respiration rate was almost linearly related to the relative growth rate. The specific respiratory costs for both growth and maintenance were highest in young fruits, but were not affected by fruit size. The average specific respiratory costs for growth and maintenance at 25°C were 3.3–3.9 mmol CO₂ g⁻¹ and 4.0 nmol CO₂ g⁻¹ s⁻¹, respectively. An increase in temperature had no effect on the specific respiratory costs for growth, while the costs for maintenance increased with a Q₁₀ of about 2. The costs for growth agreed reasonably well with theoretical estimates based on the chemical composition of the fruits but not with estimates based on only the carbon and ash content. The respiratory losses as a fraction of the total carbon requirement of a fruit changed during fruit ontogeny, but were independent of temperature and were similar for slow- and fast-growing fruits. The cumulative respiratory losses accounted for 13–15% of the total carbon requirement.     

Ethylene, a regulator of young fruit abscission

In an earlier study we reported that detached cotton flowers produced sufficient ethylene before the period of natural abscission to suggest that ethylene might be a natural regulator of young fruit abscission. The present report explores this probability further. Intact cotton (Gossypium hirsutum L.) fruits produced ethylene at rates as high as 36 μl ethylene/kg fresh wt·hr during the 2 days before they abscised. Direct measurements of ethylene in gas samples withdrawn from fruits indicated that production of 1 μl ethylene/kg fresh wt·hr is equivalent to an internal concentration of approximately 0.1 μl/l. Fumigation of fruiting cotton plants with only 0.5 μl/l caused 100% abscission of young fruits and floral buds within 2 days. This correlated with the estimated endogenous levels of ethylene. Reduced pressure, which reduced the internal levels of ethylene, delayed abscission of young fruits and leaves, a result which supports our conclusion from this study— that ethylene is one of the regulators of young fruit abscission in cotton.     

套袋对纽荷尔脐橙果实品质的影响

以纽荷尔脐橙为试材,设不同纸袋类型和拆袋时间进行套袋处理,果实成熟采收后进行品质分析。结果表明,纽荷尔脐橙适合套双层纸袋,最佳拆袋时间为采前一个月。套袋可提高果实亮度及黄色度,降低红色度,单果重有减少的倾向,果皮厚无显著差异;果实总糖与可溶性固形物含量变化不明显,总酸含量降低,糖酸比上升。综合分析表明,套袋可提高纽荷尔脐橙果实品质。     

Internal carbon dioxide and ethylene levels in ripening tomato fruit attached to or detached from the plant

The carbon dioxide and ethylene concentrations in tomato fruit ( Lycopersicon esculentum cv. Castelmart) and their stage of ripeness (characteristic external color changes) were periodically measured in fruit attached to and detached from the plant. An external collection apparatus was attached to the surface of individual tomato fruit to permit non-destructive sampling of internal gases. The concentration of carbon dioxide and ethylene in the collection apparatus reached 95% of the concentration in the fruit after 8 h. Gas samples were collected every 24 h. A characteristic climacteric surge in carbon dioxide (2-fold) and ethylene (10-fold) concentration occurred coincident with ripening of detached tomato fruit. Fruit attached to the plant exhibited a climacteric rise in ethylene (20-fold) concentration during ripening, but only a linear increase in carbon dioxide concentration. The carbon dioxide concentration increases in attached fruit during ripening, but the increase is a continuation of the linear increase seen in both attached and detached fruit before ripening and does not exhibit the characteristic pattern normally associated with ripening climacteric fruit. In tomato fruit, it appears that a respiratory climacteric per se, which has been considered intrinsic to the ripening of certain fruit, may not be necessary for the ripening of "climacteric" fruit at all, but instead may be an artifact of using harvested fruit.     

Ripening tomatoes: Ethylene,oxygen, and light treatments

Tomato fruit (Lycopersicon esculentum Mill. var. V. R. Moscow) harvested at the mature green stage were ripened by treatments with ethylene, oxygen, and oxygen plus ethylene. Treatments were made under dark and light conditions. Ethylene increased the ripening and respiration rates of the tomatoes. The fruit treated with ethylene had a general increase in beta carotene and lycopene when compared with untreated controls. The per cent acid was variable from year to year in the fruit treated with ethylene. The fruit ripened in ethylene had higher concentrations of citric acid than did the untreated controls. Treatments with oxygen decreased the reducing sugars and at the high concentrations used, had no effect on the rate of lycopene synthesis. Light treatments increased the per cent acid, reducing sugars, and color of the ripened fruit. The increase in color was related to an increase in both beta carotene and lycopene. Light treatment seemed to decrease the respiration rate of the fruit not treated with ethylene. Studies usingC¹⁴O₂ showed that this may be due to utilization of CO₂ evolved from respiration by the green fruit in photosynthesis.     

Ethylene: Response of Fruit Dehiscence to CO(2) and Reduced Pressure

These studies were conducted to determine whether ethylene serves as a natural regulator of fruit wall dehiscence, a major visible feature of ripening in some fruits. We employed treatments to inhibit ethylene action or remove ethylene and observed their effect on fruit dehiscence. CO₂ (13%), a competitive inhibitor of ethylene action in many systems, readily delayed dehiscence of detached fruits of cotton (Gossypium hirsutum L.), pecan (Carya illinoensis [Wang.] K. Koch), and okra (Hibiscus esculentus L.). The CO₂ effect was duplicated by placing fruits under reduced pressure (200 millimeters mercury), to promote the escape of ethylene from the tissue. Dehiscence of detached fruits of these species as well as attached cotton fruits was delayed. The delay of dehiscence of cotton and okra by both treatments was achieved with fruit harvested at intervals from shortly after anthesis until shortly before natural dehiscence. Pecan fruits would not dehisce until approximately 1 month before natural dehiscence, and during that time, CO₂ and reduced pressure delayed dehiscence. CO₂ and ethylene were competitive in their effects on cotton fruit dehiscence. All of the results are compatible with a hypothetical role of ethylene as a natural regulator of dehiscence, a dominant aspect of ripening of cotton, pecan, and some other fruits.     

Ethylene Production and Respiration of Postharvest Acid Citrus Fruits and Wase Satsuma Mandarin Fruit

Ethylene production and respiratory rate were examined in acid citrus fruits such as yuzu, seedless yuzu and daidai, and wase satsuma mandarin. A large amount of ethylene was produced from four varieties of citrus fruits harvested from May to July but not after September. A rise in ethylene production did not always coincide with a rise in respiratory rate. Excised tissues of fruits contained the ability of ethylene production throughout the developmental stages. The endogenous ethylene level at the ripening stage, reached the maximum when the color changed from green to yellow.     

Ethylene: role in fruit abscission and dehiscence processes

Two peaks of ethylene production occur during the development of cotton fruitz (Gossypium hirsutum L.). These periods precede the occurrence of young fruit shedding and mature fruit dehiscence, both of which are abscission phenomena and the latter is generally assumed to be part of the total ripening process. Detailed study of the dehiscence process revealed that ethylene production of individual, attached cotton fruits goes through a rising, cyclic pattern which reaches a maximum prior to dehiscence. With detached pecan fruits (Carya illinoensis [Wang.] K. Koch), ethylene production measured on alternate days rose above 1 microliter per kilogram fresh weight per hour before dehiscence began and reached a peak several days prior to complete dehiscence. Ethylene production by cotton and pecan fruits was measured just prior to dehiscence and then the internal concentration of the gas near the center of the fruit was determined. From these data a ratio of production rate to internal concentration was determined which allowed calculation of the approximate ethylene concentration in the intact fruit prior to dehiscence and selection of appropriate levels to apply to fruits. Ethylene at 10 microliters per liter of air appears to saturate dehiscence of cotton, pecan, and okra (Hibiscus esculentus L.) fruits and the process is completed in 3 to 4 days. In all cases some hastening of dehiscence was observed with as little as 0.1 microliter of exogenous ethylene per liter of air. The time required for response to different levels of ethylene was determined and compared to the time course of ethylene production and dehiscence. We concluded that internal levels of ethylene rose to dehiscence-stimulating levels a sufficience time before dehiscence for the gas to have initiated the process. Since our data and calculations indicate that enough ethylene is made a sufficient time before dehiscence, to account for the process, we propose that ethylene is one of the regulators of natural fruit dehiscence, an important component of ripening in some fruits. Our data also suggest a possible involvement of ethylene in young fruit abscission.     

Ripening Physiology of Fruit from Transgenic Tomato (Lycopersicon esculentum) Plants with Reduced Ethylene Synthesis

The physiological effects of reduced ethylene synthesis in a transgenic tomato (Lycopersicon esculentum) line expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme have been examined. Fruit from the transgenic line 5673 ripen significantly slower than control fruit when removed from the vine early in ripening. In contrast, fruit that remain attached to the plants ripen much more rapidly, exhibiting little delay relative to the control. Ethylene determinations on attached fruit revealed that there was significantly more internal ethylene in attached than detached fruit. The higher ethylene content can fully account for the observed faster on-the-vine ripening. All of the data are consistent with a catalytic role for ethylene in promoting many, although not all, aspects of fruit ripening. Biochemical analyses of transgenic fruit indicated no significant differences from controls in the levels of ACC oxidase or polygalacturonase. Because transgenic fruit are significantly firmer than controls, this last result indicates that other enzymes may have a significant role in fruit softening.     

Response of Developing Apple Fruits to Ethylene Treatment

Knee, M., Hatfield, S. G. S. and Bramlage, W. B. 1987. Responseof developing fruits to ethylene treatment.—J. exp. Bot.38: 972–979. Fruits of apple (Malus domestica Borkh. cv. Cox's Orange Pippin)were treated with various concentrations of ethylene usuallyfor 48 h to determine their response in relation to stage ofdevelopment. The main response recorded was the reduction byethylene of the delay in onset of rapid ethylene production(DEP) in individual fruits. Early in development low concentrationsof ethylene had little effect but DEP was progressively reducedby concentrations up to 10⁷ mm³ m^–3. As the fruit approachedthe natural onset of rapid ethylene synthesis concentrationsof 10² and 10³ mm³ m^–3 became increasingly effective.Increasing the duration of treatments with a fixed concentrationreduced DEP proportionately. Delay after harvest in applyinga 48 h treatment had little effect on the relation between DEPand concentration of ethylene applied. Although resistance todiffusion of gas in fruits increased during fruit developmentthis resistance was never large enough to affect the relationof concentration and response. Key words: ethylene, fruit ripening, Malus domestica