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Open access

Jorge B. Retamales and Martin J. Bukovac

Abstract

AC 94377 (alone and in combination with an auxin), GA3, and BA were evaluated for induction of parthenocarpy and subsequent retention of sour cherry (Prunus cerasus L. ‘Montmorency’) fruit. The persistence of AC 94377-treated fruit was enhanced by addition of CFPA or NAA, persistence and growth being greatest with AC 94377 (3.0 × 10−3 m) + CFPA (7.5 × 10−5 m). CFPA alone (7.5 × 10−5 m) often prevented abscission of flowers, but failed to induce significant fruit growth. Parthenocarpic fruit weighed 30-40% less than seeded fruit. Abscission of parthenocarpic fruit occurred primarily during June drop, and was reduced by an additional application of AC 94377 + CFPA with or without GA3 3 weeks after bloom. AC 94377 and NAA sprayed 2 and 3 weeks after full bloom did not affect the magnitude of June drop of open-pollinated fruit. The rate of fruit abscission was related to time after application, presence or absence of seeds, and relative position between seeded and parthenocarpic fruit. When AC 94377, GA3, and CFPA were applied in lanolin paste to defruited pedicels, only mixtures including CFPA reduced the abscission rate significantly. Chemical names used: l-(3-chlorophthalimido)-cyclohexanecarboxamide (AC 94377); 2-chloro,4-fluorophenoxyacetie acid (CFPA); N-(phenylmethyl)-lH-purin-6-amine (BA); gibberellic acid (GA3); 1-naphthaleneacetic acid (NAA).

Open access

Jose Eduardo O. Lima and Frederick S. Davies

Abstract

Secondary-fruit yellowing (SFY) of navel orange [Citrus sinensis (L.) Osbeck], a major cause of summer fruit drop, was induced artificially by girdling the stem 5 to 10 cm from the fruit. Girdling from 26 to 28 May 1982 increased ethylene levels at the stylar end and induced SFY in 90% of treated fruit. Girdling at other times, or at 30 to 45 cm from the fruit, however, caused minor SFY, particularly if leaves were present between the fruit and girdled area, indicating some material is produced by the leaves that reduces the incidence of SFY. Increase of ethylene levels and cellulase activity in the abscission zone of the secondary fruit prior to increases in the abscission zone of the primary fruit indicate that secondary-fruit abscission leads to primary fruit abscission. Water stress or changes in nonstructural carbohydrate levels within the leaves induced by branch sawing did not cause SFY. Application of 2,4-dichlorophenoxyacetic acid (2,4-D) prior to or during induction lessened the severity of SFY and significantly decreased ethylene levels at the stylar end of the fruit.

Free access

Kiyoshi Banno and George C. Martin

Olive fruit harvest by mechanical shaking continues to be limited by poor fruit removal - less than 60% removal for most varieties. Whereas foliar spray of ethylene releasing compounds such as ethephon increases fruit removal percent, excessive leaf loss following treatment precludes commercial acceptance of the treatment. A classic case of serendipity has led to the testing of phosphorus as an olive fruit loosening agent. Na2 HPO4 at 25 mM applied via the cut stem of explants leads to massive leaf and fruit abscission. When the P source is applied at 100 mM foliar spray, fruit removal is accomplished with minimal leaf loss. Results of this investigation will cover P source, concentration, genera with abscission response and some indication of mechanism of action.

Free access

Gene Lester

Hybrid, non-netted, green-fl esh, honeydew muskmelon fruit physiological maturity occurred by 40 days after anthesis (DAA). Fruit maturity was determined by major increases in quality attributes: moisture content, firmness, soluble solids concentration, weight, volume, and qualitative and quantitative changes in glucose, fructose, and sucrose content. Fruit ripening occurred between 40 and 50 DAA as determined by maximized changes in the aforementioned quality attributes, and by fruit abscission at 50 DAA. Fruit senescence begins with decreases in: quality attributes, hypodermal-mesocarp plasma membrane H+-ATPase (E.C. 3.6.1.3) activity, and protein content, and by increases in: the total free sterol: total phospholipid ratio, and hypodermal-mesocarp lipoxygenase (E.C. 1.13.11.12) activity. Delineated growth and maturation physicochemical data of hybrid honeydew muskmelon fruit should be beneficial to the commercial harvest of mature fruits, which is necessary for maximizing honeydew fruit quality, extending shelf-life, and enhancing consumer satisfaction.

Free access

Ramon A. Arancibia and Carl E. Motsenbocker

`McIlhenny Select' (easy detachment) and `Hard Pick' are two lines of tabasco pepper (Capsicum frutescens L.) that differ in the fruit detachment characteristics. Cellulase (Cx) and polygalacturonase (PG) activity, extracted from the fruit abscission zone, correlated inversely with the force needed to separate the fruit from the pedicel. A trend of higher Cx and PG is associated with the lower detachment force in the McIlhenny Select line. Differences in the fruit cell wall protein profile between both lines occurred during ripening. Two bands of 23 kDa and 40 kDa were higher in `McIlhenny Select'. A band of approximately 30 kDa was higher in `Hard Pick', while a band of ≈70 kDa increased in both lines. Isolation and characterization of these bands as well as Cx and PG is needed to understand the factors affecting fruit detachment in tabasco pepper.

Free access

Eric A. Currv

These studies with apple (Malus domestica Borkh.) spur tissues were conducted to investigate the mechanism whereby NAA may stimulate fruit abscission in the spring but acts to prevent fruit drop in the fall. NAA-induced ethylene evolution from `Delicious' spurs in vivo was similar to that evolved from excised leaf and fruit tissues that later were treated in the laboratory and incubated in darkness at 20C. The peak in ethylene production occurred 24 hours after treatment at 30C, 48 hours after treatment at 20C, and production was still increasing 72 hours after treatment at 10C. Leaf tissue showed the greatest induction of ethylene from NAA followed by fruit and petiolar tissues. Induction was greatest early in the season and declined steadily until about “June drop.” After this time, none of the tissues showed significant capacity for ethylene induction. Chemical names used: 2-(1 -naphthyl) acetic acid (NAA).

Free access

Carl E. Motsenbocker and Kay P. Gersch

Field and greenhouse studies were conducted to examine fruit detachment force and plant parameters of two strains of Tabasco (Capsicum frutescens) at different stages of maturity. The detachment force of mature red `McIlhenny Select' at the fruit-receptacle detachment area was less than that of breaker and mature green fruit. `McIlhenny Select' separated cleanly at all stages of maturity. A wild type Tabasco strain `HP' did not abscise at the red mature stage; fruit detachment force was greater than that of `McIlhenny Select'. The detachment force of mature green and breaker `HP' fruit were similar to those of `McIlhenny Select' at the same stage of maturity. Fruit weight, length, and width of the two tabasco strains were not different. The utility of the `McIlhenny Select' and `HP' strains for physiological studies of pepper fruit abscission will be discussed.

Free access

Duane W. Greene, Wesley R. Autio, and Paul Miller

Postbloom sprays of BA thinned `McIntosh', `Delicious', `Golden Delicious', `Mutsu, `Empire', and `Abas' apples. BA at 75 to 100 mg·liter-1 was equal to NAA at 6 to 7.5 mg·liter-1 or carbaryl at 600 to 800 mg·liter-1. BA increased fruit size, flesh firmness, and soluble solids concentration (SSC) on all cultivars evaluated. Since BA is applied during the time when cell division is occurring, it is concluded that the increased fruit size and flesh firmness were due to Increased cell numbers. Increased SSC was not due solely to increased leaf: fruit ratio. Thinning with BA was additive with other chemical thinners and no interactions were found on fruit abscission. In most eases, BA increased return bloom. Chemical names used: N-(phenylmethyl)1H-purine-6-amine [benzyladenine (BA)]; 1-naphthaleneacetic acid (NAA); 1-naphthalenyl methylcarbamate (carbaryl); butanedioic acid mono(2,2dimethylhydrazide (daminozide); (2-chloroethyl)phosphonic acid (ethephon).

Open access

Jeff W. Daniell and R. E. Wilkinson

Abstract

Mature peach trees (Prunus persica (L.) Batsch. cv. Southland) were treated with 0, 1.73, 2.42, and 3.11 Mmoles/1 of (2-chlorethyl)phosphonic acid (ethephon) and ethylene evolution was measured up to 9 days after treatment. Ethephon caused a marked increase in ethylene evolution, a sharp decrease in the breaking force of fruit abscission, and a pronounced increase in leaf abscission. Ethylene evolution was higher in leaves than fruits. In general, ethylene from tissue explants containing the abscission zone of fruits was higher than that of explants from the side of fruits from treated trees. However, it was postulated that ethylene has an overall affect on all tissue with subsequent abscission rather than a direct effect on the abscission zone of leaves and fruits of peaches.

Free access

Alireza Talaie*, Ali Gharaghani, and Mohammad Ali Asgari

In this research the effect of four clonal rootstocks (B9, M9, M26, and MM106) on growth characteristics, flowering and fruiting, and fruit quality and quantity of `Golden Smoothee' apple (Malus × domestica Borkh.) were studied during 2001 and 2003. Trees were 8 years old at the beginning of study. Experiments were planned in randomized complete-block design with four treatments (four rootstocks) and four replications. Rootstocks had significant effects on all growth characteristics. The highest tree height, shoot growth, and tree cross-sectional area were found on MM106; with B9 was the least and M9 and M26 were intermediate. The effect of year, and interaction of year on rootstocks were nonsignificant. Rootstock has highly affected flowering and fruiting characteristics. The highest flowering efficiency related to M9 and B9. The highest primary and secondary fruit set and fruit set efficiency found with M9 and M26. The highest preharvest fruit abscission observed with M26. The M9 had the least preharvest fruit abscission. Yield of M9 was the highest and B9 was the least. The M9 has the most yield efficiency and MM106 had the least. Effect of year was significant in many characteristics related to flowering and fruiting. Generally, trees had better conditions in first year. Among fruit quantitative treatments, rootstock only affected fruit weight significantly. Fruit harvested from B9 had the least weight and other rootstocks had similar fruit weight. Generally rootstock had no noticeable effect on fruit quantity and quality.