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  • Author or Editor: M. J. Bukovac x
  • Journal of the American Society for Horticultural Science x
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Abstract

Levels of gibberellin (GA)-like substances were determined in sour cherry (Prunus cerasus L.) seed in relation to fruit development using the cucumber and dwarf pea bioassays. Two GA-like substances were found; one was soluble in ethyl acetate and the other, a more polar substance, in butanol. Concentrations of both substances increased to a maximum 14 days after anthesis and then decreased and remained low during Stage III. Changes in seed GA-like substances coincided with development of the seed components, nucellus, endosperm, and embryo, and the early enlargement of the pericarp, but not with subsequent development of the pericarp. Both the ethyl acetate- and butanol-soluble GA-like seed substances chromatographed at a lower Rf than GA3. The butanol-soluble component is probably not a glycoside, since no ethyl acetate-soluble GA was released on hydrolysis. The butanol-soluble component resembles GA32 in polarity, partitioning characteristics and Rf.

Open Access

Abstract

Dehydrogenase, acid phosphatase, and peroxidase activities were localized histochemically in the lower (pedicel-fruit) abscission zones of sour (Prunus cerasus L.) and sweet (Prunus avium L.) cherry fruits. Highest enzyme activity generally occurred at the juncture of the receptacle and fruit tissues; the region where separation occurred. Both species had a similar peroxidase isozyme pattern; however, 2 bands in sweet cherry had lower intensities than sour cherry. The implications of localized activities of these enzymes in cherry fruit abscission are discussed.

Open Access

Abstract

An indole-3-acetic acid oxidase system was detected and characterized in extracts of immature peach seed (Prunus persica (L) Batsch, cv. Redhaven). The enzyme had a pH optimum of 4.5 to 5.0 and required Mn2+ and 2,4-dichlorophenol for optimum activity. The reaction product appeared to be 3-methyleneoxindole. Catechin, a natural polyphenol, was isolated from peach seed. It inhibited the IAA oxidase system and had a synergistic effect on IAA activity in the Avena coleoptile straight growth assay. Kinetic studies demonstrated that the catechin inhibition was non-competitive with substrate.

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

Abstract

Fruit removal force (FRF) of sour cherry, Prunus cerasus L. ‘Montmorency’, was markedly reduced by foliar sprays of 2-chloroethylphosphonic acid (CEPA) applied 3-15 days prior to harvest. The maximum reduction in FRF occurred with CEPA 6 days after treatment for all concentrations (500, 1000, 2000 and 4000 ppm). In addition to a reduction in FRF the dispersion of the individual FRF values was significantly reduced. Fifty per cent fruit removal with the 500 ppm treatment was accomplished by a force of 171 g compared to 434 g for the control. High concentrations (2000 and 4000 ppm) of CEPA caused serious phytotoxicity, such as leaf abscission, terminal dieback, gummosis and enlarged lenticels. Trees of low vigor or the spurs and terminal growth of weak wood were most seriously affected. Fruits on branches treated with CEPA appeared to be advanced in maturity. There was a striking delay in anthesis in the spring following summer application of 4000 ppm CEPA. No significant delay occurred at lower concentrations. Ascorbic acid (20,000 ppm), iodoacetic acid (300 ppm) and salicylic acid (500 ppm) were either not effective or less active than CEPA.

Open Access