GA3-treated Fruit Research Articles

Effect of GA3 Bloom Sprays on Fruit Set and Yield of Rabbiteye Blueberry

Field and growth chamber experiments, and grower trials, were conducted to determine the effects of GA3 sprays on yield and fruit quality of rabbiteye blueberry (Vaccinium ashei Reade) in northern Florida and southern Georgia. Multiple GA3 sprays at various stages of flower development increased fruit set and yield in field experiments (Florida) and grower trials (Georgia) when compared to controls. Nonpollinated rabbiteye flowers sprayed with GA3 had greater percent fruit set and delayed fruit development compared to hand pollination. Percent fruit set and average fruit weight were reduced at 21C night temperature when compared to 10C night temperature for both hand-pollinated and GA3-treated fruit. Overall, yields were increased by multiple applications of GA3 during bloom, but average fruit size was reduced and the fruit development period was lengthened.

745 PB 079 SINK SIZE IN GAs-TREATED AND POLLINATED RABBITEYE BLUEBERRY FRUITS

Exogenous applications of GA, have induced pathenocarpic fruit set in blueberry; however, size of GA,-treated fruit is smaller than pollinated fruit. The small fruit size in GA3-treated fruit may be related to either cell number and/or cell size. Thus, these parameters were examined throughout development in pollinated, non-pollinated and GA3-treated fruits. Fruit growth followed a double sigmoid pattern. During Stage I (0-25 DAA), fruit size in GA,-treated, pollinated, and non-pollinated fruits averaged 0.33, 0.39, and 0.16 g, respectively. There was little change in fruit size in Stage II (25-45 DAA). At ripening, fruit size averaged 1.7 g for GA,-treated and 2.6 g for pollinated fruits. Non-pollinated fruit abscised in Stage II. At anthesis, mesocarp cell number averaged 9910 cells per median cross sectional area and remained constant up to ripening. In Stage I, cell size in G A3-treated and pollinated fruits increased 7X and 9X respectively. Cell size in both fruit types increased 1.5X and 2.8X during Stage II and Stage 111, respectively. Fruit cell number was set at anthesis and differences in fruit size were due to differences in cell ellongation in Stage I.

CARBOHYDRATE METABOLISM IN GA3-TREATED AND POLLINATED RABBITEYE BLUEBERRY FRUITS.

Carbohydrate metabolizing enzymes and carbohydrate accumulation were examined in pollinated, non-pollinated and GA3-treated blueberry fruit. Our hypothesis was that GA3 induces fruit set in blueberry by increasing the carbohydrate metabolizing enzyme activity in the ovary with a subsequent increase in carbohydrate mobilization. FW of non-pollinated fruits increased little between 0-45 days, when abscission occurred. FW of GA3-treated and pollinated fruits increased from 20 mg at anthesis to 1 and 2 g, respectively, at ripening. Insoluble invertase activity decreased from 15 μmol gFW-1 h-1 at anthesis to 3 μmol gFW-1 h-1 at 45 DAA for GA3-treated and pollinated fruits, and 9 μmol gFW-1 h-1 in non-pollinated fruits. Soluble invertase was undetectable in any treatment from 0 to 45 days, but rose sharply, averaging 57 μmol gFW-1 h-1 at ripening for both GA3-treated and pollinated fruits. No consistent correlation was found between ovary carbohydrate concentration and fruit growth among treatments. Differences in fruit set and size among treatments were not due to differences in enzyme activity and subsequent differences in carbohydrate accumulation.

Influence of Seeded Fruit on Seedless Fruit Set in Japanese Persimmon cv. Fuyu (Diospyros kaki L. f.).

The influence of seeded Japanese persimmon cv. Fuyu (Diospyros kaki L. f.) fruit on the setting of seedless ones achieved by 1) hand-pollination; 2) open-pollination; 3) non-pollination; 4) ringing of the bearing shoot; and 5) gibberellin-3 (GA3) application was investigated to clarify the factors affecting seedless fruit set and the inconsistency of GA-treated fruit set.The number of seeds per fruit and the degree to which seedless fruit abscised on the same tree were significantly different among trees. However, a highly significant, positive linear relationship (r= 0.77) existed between the two parameters. No abscission of seedless fruits on ringed shoots occurred until the girdle region had healed. On non-pollinated trees, seedless fruit set increased as the concentration of GA3 was increased. However, more seedless fruit dropped from pollinated trees than from non-pollinated trees, although seedless fruits of both plots were treated with the same concentration. This induction of abscission is ascribed to the competition between seedless fruit and seeded fruit on the same tree. A major factor to fruit set was the competition among fruits; the competitive advantage of seeded fruit over parthenocarpic ones is the decisive factor whether or not GA-treated 'Fuyu' fruits abscise.

カキの果実品質に及ぼす開花日, 種子, GA処理ならびに結果部位の影響

The effects of bloom date, seediness and location of the fruit in the foliar canopy on the fruit quality of persimmon cv. Maekawa-Jiro and the relation between GA treatment and fruit quality of persimmon cv. Jiro were studied.1. Flowers which bloomed 12d later (delayed flowers) than those of the main flower population (normal flowers), gave rise to small, poorly colored fruits having low soluble solids content.2. Fruits borne high and on the outer periphery of the foliar canopy developed better color and had high soluble solids content as compared to those borne low and in the interior part of the canopy. The width of epidermal cracks at the apex of fruits derived from delayed flowers were as wide as cracks on fruits which developed from normal flowers. Seeded fruits, especially those borne on the periphery of the canopy and exposed to high light intensities, possessed wide apical cracks. Conversely, on trees which produced predominantly seedless fruits, the apical cracks were narrow, independent of their location in the canopy.3. On trees which produced many seeded fruits, the seedless ones were small, slow in developing color, and possessed low soluble solids content as compared to seeded fruits, whereas, on trees bearing fruits with a few seeds, seedless and seeded fruits were similar in size, color and soluble solids content.4. Hand pollination of normal and delayed ‘Jiro’ flowers increased the percentage fruit set. Gibberellic acid (GA3) applications to pollinated and nonpollinated flowers improved fruit set but decreased seed count/fruit compared to untreated fruits. GA-treated fruits were smaller and the widths of apex crackings were narrower than those of untreated ones.

Fruit Age and Gibberellic Acid Effect on Epicuticular Wax Accumulation, Respiration, and Internal Atmosphere of Navel Orange Fruit

Abstract Relationships among fruit age, epicuticular wax, weight loss, internal atmosphere composition, and respiration were investigated in mature ‘Washington’ navel orange fruit [Citrus sinensis (L.) Osbeck]. Fruit epicuticular wax, internal CO2, and internal C2H4 increased, whereas as the season advanced, weight loss during storage and respiration decreased. Concomitantly, fruit conductance to CO2 was reduced. GA3 (10 ppm) application prior to fruit color break reduced the increase in epicuticular wax and thereby delayed the decrease of CO2 conductance, resulting in less of an increase in internal CO2. GA3-treated fruit were not consistently different for other parameters evaluated. Chemical name used: lα,2β,4aα,4bβ,10β)-2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-l,10-dicarboxylic acid l,4a-lactone (gibberellic acid).

Fruit Age and Growth Regulator Effects on the Quantity and Structure of the Epicuticular Wax of ‘Washington’ Navel Orange Fruit

Abstract Changes in ‘Washington’ navel orange [Citrus sinensis (L.). Osbeck] fruit epicuticular wax quantity and structure were followed during fruit development, maturation, and senescence. Whole-tree sprays of 10 ppm GA3, 16 ppm 2,4-D, and a combination of GA3 (10 ppm) plus 2,4-D (16 ppm) were made at fruit color-break, and effects on wax were examined at 4-week intervals. The total epicuticular wax produced per fruit and per unit of fruit surface area increased with time on control and on treated fruit. GA3-treated fruit produced significantly lower amounts of wax per unit of surface area than did control or fruit treated with 2,4-D alone. Total epicuticular wax per unit of fruit surface area of the control was similar to that of the 2,4-D-treated fruit until late in the season, when that of the control significantly exceeded that of the 2,4-D treatment. Wax per unit of fruit area of the GA3-treated fruit was not significantly different from that of the GA3 plus 2,4-D-treated fruit until late in the season, when GA3 plus 2,4-D treatment resulted in significantly higher values. Scanning electron microscopy revealed significant changes in surface morphology and ultrastructure of the epicuticular wax during fruit development, maturation, and senescence. Control fruit and 2,4-D-treated fruit were similar, but GA3 delayed ultrastructural changes that were seen in the control fruit. The incidence of ‘sticky’ rinds was reduced significantly by GA3 treatment, and ‘sticky’ rind surface wax had a structure similar to that of senescing surfaces. Chemical names used: (2,4-dichlorophenoxy)acetic acid (2,4-D); gibberellic acid (GA3).

Levels of Pectic Substances and Calcium in Gibberellic Acid-treated Sweet Cherry Fruit1

Abstract Foliar applications of gibberellic acid (GA3) to mature ‘Lambert’ sweet cherry trees (Prunus avium L.) about 21 days before harvest increased fruit weight (fresh and dry), soluble solids (SS), alcohol-insoluble substances (AIS) (both concentration and per fruit), ash weight, and fruit firmness at harvest. Application of GA3 did not affect concentrations of ethylene diamine-tetraacetic acid (EDTA) or pectinase-soluble pectins and fruit Ca. GA3-treated fruit had lower concentrations of water-soluble pectins and reduced surface pitting. Fruits sampled at 3–7 day intervals (starting about 21 days before harvest) from control and GA3-treated trees showed that as an average response over a 29-day sampling period GA3 increased fruit weight, firmness, AIS concentration, AIS per fruit, pectinase-soluble pectins, and decreased water-soluble pectins. Neither total, residual, or soluble fruit Ca were affected by treatment with GA3. Fruit Ca levels remained constant, on a per fruit basis, during the last 3 weeks of fruit maturation but Ca concentration, expressed as fresh or dry weight, decreased as a result of increased fresh and dry weight. Higher Ca levels were not associated with firmer fruit (comparing GA3 and nontreated fruit), but were correlated positively with firmness in nontreated fruit.

Some Growth Regulator Effects on Fruit Quality, Mesocarp Composition, and Susceptibility to Postharvest Surface Marking of Sweet Cherries1

Abstract Gibberellic acid (GA3) sprays applied approximately 4 weeks before harvest reduced postharvest surface marking of ‘Van’ and ‘Lambert’ sweet cherries (Prunus avium L.). Surface pitting was reduced more consistently than was visible bruising. GA3-treated fruits were larger and firmer when harvested at a prescribed color maturity. Mesocarp tissue of treated fruits was higher in alcohol insoluble solids, higher in dry weight and contained less nitrogen per unit of fresh or dry weight. Ethephon applied a few days before harvest reduced fruit removal force but did not consistently reduce the incidence of bruising or surface pitting. ‘Lambert’ fruits picked without stems developed more surface pitting than stemmed fruits. It is proposed that GA3 improves postharvest fruit condition by more than one mechanism. Increased fruit firmness may reduce the tendency to bruise but pitting appears to be suppressed by some other physiological effect of the GA3 treatment.

ナルトミカンの果皮組織における<i>n</i>-ヘキサナールの生成特に果皮の老化と生理障害 (果皮黄斑症) に関連して

n-Hexanal was found in macerated rind tissues of Naruto (Citrus medioglobosa hort. ex Tanaka). Hexanal formation was thought to be catalyzed by enzyme system. In this reaction, optimum pH was about 4.5.Rates of hexanal formation were closely associated with the degree of degreening of the fruit rind: their order was CEPA-treated fruits>outside fruits>inside or GA-treated fruits. There was a high rate of the hexanal formation in the fruit rind affected by ‘rind yellow spot’, a physiological rind disorder of Naruto, compared to healthy fruit rind. The hexanal formation was influenced by ambient temperature to which fruits had been exposed. A higher rate was observed on fruits held at 20°C than those held at 5°C. After transfer of fruits from 5°C to 20 °C, the rate increased within 3-4 hours.Possible physiological importance of the hexanal formation was discussed in relation to aging of the rind and ‘rind yellow spot’ which occurs in accordance with aging of the rind.

Effects of GA3 on Puffing and Levels of GA-like Substances and ABA in the Peel of Satsuma Mandarin (Citrus unshu Marc.)1

Abstract GA3 was applied to satsuma mandarin fruit at the concn of 100 ppm 25 and 35 days before harvest. The percentage puffy fruit was greater in the untreated than in both treated plots at harvest time. Chlorophyll was more abundant in the peel of treated fruits than in those of the untreated. GA-like substances in the peel decreased rapidly in untreated fruit in early September, then leveled off toward maturity. They increased more than 40 times in the flavedo of treated fruit as compared with the control. ABA content in the untreated peel increased gradually during early fruit enlargement and then increased rapidly to a very high value during maturity. The ABA content in the peel of GA3-treated fruit did not increase at the same rate as the control. Sugar content in the peel was depressed by GA3 application.

Respiration Rate and Acidity in Parthenocarpic and Seeded Conference Pears

SummaryGibberellin induced parthenocarpic Conference pears started to grow sooner than seeded or naturally parthenocarpic fruits, but their growth rate declined earlier. At harvest the seeded fruits were bigger than GA3-treated and naturally parthenocarpic fruit.Respiration rates in peel and pulp of GA3-treated pears and in the peel of naturally parthenocarpic fruit were higher than in the controls. Respiration rates of peel were always higher than those of pulp or core.Within four weeks of petal fall the titratable acidity of GA3-treated fruits was somewhat higher than that of seeded or naturally parthenocarpic controls. In all treatments acidity fell rapidly after this time and declined further until harvest.

Endogenous Auxin and Gibberelliu-like Activity in Highbush Blueberry Flowers and Fruit1

Abstract ‘Coville’ and ‘Jersey’ blueberry (Vaccinium) flowers and fruit from screened bushes treated with 500 ppm of gibberellic acid (GA) at bloom and from bushes subject to insect pollination were sampled and measured at weekly intervals. Extracts of these organs were partially purified by chromatographic separation on paper, then bioassayed for auxin and gibberellin-like (GA-like) activity. Endogenous levels of both auxin and GA-like substances were higher in ‘Jersey’ than in ‘Coville’ flowers. Auxin concentration in unpollinated flowers was 4 times greater in ‘Jersey’ than in ‘Coville’. A large increase in extractable auxin followed GA treatment in both cultivars. The increase in extractable auxin coincided with the more rapid initial growth rate characteristic of GA-treated fruits. Auxin level coincided with fruit growth rate much better than did level of GA-like substances. By 6 weeks after GA treatment, GA-like substances in the fruits decreased to a level no higher than that in pollinated fruits.

The growth of apricot fruit. II. The effects of temperature and gibberellic acid

The effect of temperature and gibberellic acid (GA3) applications on apricot fruit have been determined by measurements of fruit size and shape, mesocarp cell number, size, and shape, and endogenous gibberellin. Application of heat during the first 10 nights after anthesis increased the initial growth rate of fruit and of cells in the mesocarp and produced more rapid cell division in this tissue. It did not affect final fruit size or the number and diameter of cells in the mesocarp. Higher temperatures did, however, hasten maturity of fruit. GA3 perfused into branches before anthesis produced an increased drop of flower buds and fruit, raised the ratio of flower buds to leaf buds initiated that season, and resulted in elongated pedicels. Initially, fruit growth rate was increased by GA3, but subsequently it was depressed and final size was below normal. These effects on fruit size were mainly due to effects on the rate of cell division. Some differences were noted in the dimensions of cells but final radial cell diameter did not differ from untreated fruit. GA3-treated fruit ripened sooner than controls. Neither heating nor GA3 treatments affected the level of endogenous gibberellin-like substances in the fruit or their RF on paper chromatograms. There were no significant interactions between temperature and gibberellin in any parameter of apricot fruit growth.