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  • Author or Editor: V. A. Wittenbach x
  • Journal of the American Society for Horticultural Science x
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Abstract

Physiological parameters of abscission at the zone between the pedicel and fruit of the sour (Prunus cerasus L. ‘Montmorency’) and sweet (Prunus avium L. ‘Windsor’) cherry were investigated using fruit explants. 3-Indoleacetic acid, 2-(chloroethyl)phosphonic acid (ethephon), gibberellin A3, and abscisic acid hastened abscission (during Stage III) in sour cherry, while only ethephon enhanced abscission in the sweet cherry. Cycloheximide blocked abscission in both sour and sweet cherry and negated the effect of ethephon. Explants prepared from fruits during various stages of development exhibited a differential response to ethylene. Abscission in the sour cherry was enhanced by increasing temperature and was greater in dark than in light, while both high CO2 and low O2 levels delayed abscission.

Open Access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) significantly reduced the fruit removal force (FRF) at the lower abscission zone of ‘Montmorency’ sour (Prunus cerasus L.) and ‘Windsor’ sweet (Prunus avium L.) cherry fruit near maturity. No qualitative differences were detected in abscission layer development as a result of ethephon treatment. The primary effect was an acceleration of fruit separation following a pattern similar to that observed in the control. Separation in both treated and control sour cherry fruit was preceded by a loss of pectin and polysaccharides and a loss of cellulose orientation in the walls of cells comprising the abscission layer. Although separation in treated sweet cherry fruit was more extensive than in the control at maturity, it was still localized as in nontreated fruit and was not preceded or accompanied by a change in pectin, cellulose, or polysaccharides in the abscission layer. No effect of ethephon was observed on the upper abscission zone for either species through fruit maturity. Ethephon caused a dramatic increase in ethylene evolution from cherry fruit.

Open Access

Abstract

Abscission of maturing sweet cherry fruit (Prunus avium L. cv. Windsor) occurred at 2 different abscission zones, depending on the stage of fruit development. Immature fruit abscised at the upper zone between the pedicel and peduncle; mature fruit abscised at the lower zone between the fruit and receptacle. Separation in the abscission layer began directly above the stony pericarp and resulted in the formation of a cavity. Later separation occurred at the fruit : pedicel indentation and extended through the abscission layer toward the vascular bundles. Abscission involved the fracturing of cell walls as well as wall separation. There was no evidence of change in pectins, cellulose or other polysaccharides in the cell walls of the abscission layer prior to or during fruit separation. No starch accumulation in the abscission zone or lignification of tissue adjacent to the abscission layer was observed through fruit maturity.

Open Access

Abstract

Mechanical injury to the seed of immature sour cherry (Prunus cerasus L., cv. Montmorency) fruit caused an immediate and marked increase in ethylene evolution followed by abscission of the fruit at the peduncle: pedicel zone. Ethylene evolution was induced when the seed, but not the pericarp, was injured. The magnitude of ethylene evolution was related to stage of fruit development at time of injury, and was most pronounced when the nucellus was the dominant tissue in the seed. Ethephon (500 and 1000 ppm) also caused immature fruits to abscise and abscission was preceded by embryo abortion. The site of ethephon-induced fruit separation differed depending on stage of fruit development at time of treatment. Fruit separation occurred at the peduncle:pedicel abscission zone when immature fruits were treated, and at the pedicel fruit zone when mature fruits were treated. The role of ethylene in the abscission of immature sour cherry fruit is discussed.

Open Access

Abstract

Peroxidase activity was demonstrated in the abscission zone and adjacent tissues of sour cherry fruit (Prunus cerasus L., cv. Montmorency) from Stage I of fruit growth to maturity. Activity was markedly greater in the receptacle and abscission zone, than in the fruit tissues. A difference was observed histochemically in the peroxidase of the abscission layer from that of the adjacent tissues. Moreover, peroxidase activity in the abscission zone increased to a maximum at a stage of development coinciding with the initiation of the separation phase. This increase in activity was accompanied by an increase in 2 of the major isoenzymes and the appearance of a third. The relationship between changes in peroxidase and abscission in fruit explants was less clear. Ethylene and ethephon had no significant effect on total peroxidase activity; however, ethylene appeared to increase the activity of a basic isoenzyme. Cycloheximide treatment decreased total and isoenzyme activity. Lowering the endogenous ethylene level did not reduce total activity, although the activity of a basic isoenzyme was decreased.

Open Access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) applied as a foliar spray to sweet cherry trees within 2 weeks of fruit maturity promoted fruit abscission at the lower (fruit:pedicel) zone, as indexed by a reduction in the fruit removal force (FRF). There was no significant effect, at the concn studied, on abscission at the upper (pedicel:peduncle) zone. Promotion of abscission with ethephon was time and concn dependent. Ethephon concn of 100 to 1000 ppm were effective with a greater response from the higher concn. Absorption periods of 4 and 24 hr resulted in responses equal to 73 and 94% of that observed when ethephon was present for the entire experimental period. Of 9 sweet cherry cultivars evaluated, all responded similarly in terms of reduction in FRF. Ethephon enhanced fruit enlargement and pigmentation when applied early in Stage III of fruit growth. The increase in wt was most pronounced in the fleshy pericarp tissue.

Open Access