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- Author or Editor: G. E. Stembridge x
Abstract
The cytokinin 6-benzyladenine (BA) and gibberellins A4 + A7 (GA4+7), but not GA3, increased the fruit length-diam (L/D) ratio of ‘Delicious’ apples. Prominence of the points near the fruit calyx was increased more by BA than by GA4+7, but increased most when the 2 were combined. Sprays during bloom were more effective than either postbloom or prebloom sprays.
A bloom spray combining GA4+7 and BA at 100 ppm each decreased fruit set of open pollinated flowers in one year, but not in another. Concentration of 50 ppm or less altered fruit shape without any significant effect on the number of seed, fruit set, firmness, or fruit size.
Abstract
A 500 ppm gibberellin A3 (GA) spray applied shortly after full bloom to unemasculated peach flowers caused some fruit to develop parthenocarpically. Nonparthenocarpic fruit sprayed with GA were similar to parthenocarpic fruit in their elongated shape and advanced maturity, and dissimilar to unsprayed control fruit. The applied GA, rather than a lack of ovule development, is therefore primarily responsible for alterations in shape and maturity of parthenocarpic peaches.
Abstract
A single-value estimate of maturity response and an independent estimate of the thinning response to treatment can be determined from detailed harvest records. Thinning index is estimated from the total number of fruit per tree; maturity response is estimated from the weighted-average harvest date.
Abstract
Several peach varieties were sprayed with 3-chlorophenoxy-α-propionamide (3-CPA) at different stages of fruit development. The timing of the application was critical, and varieties differed greatly in their thinning response. The ‘Ranger’ variety was thinned with ease, but attempts to thin ‘Cardinal’ with 3-CPA were unsuccessful. Fruit thinning apparently increased the cold hardiness of the flowers during the following bloom period. Several spray additives were found to increase the thinning effectiveness of 3-CPA.
Abstract
Succinic acid, 2, 2-dimethyl hydrazide (Alar) sprays were applied at 3,000 and 10,000 ppm to vigorous young ‘Delicious’ apple trees in which yields were limited by insufficient bloom. Sprays applied at the high concentration after harvest in 1965 not only delayed bloom the following spring but also caused mortality of fruit buds and individual flowers. Alar sprays applied shortly after full bloom in 1966 retarded shoot elongation more effectively than the postharvest sprays applied the previous fall, but both were about equally effective in retarding fruit growth and promoting fruit bud formation during the 1966 growing season. The postharvest sprays caused an oblate fruit shape the following year. Alar sprays increased fruit firmness, but did not significantly affect soluble solids or titratable acids. The Alar-induced flowering was responsible for large increases in yield in 1967. Trees which were induced to flower profusely had a very light return bloom in 1968.
Abstract
Bloom or postbloom sprays of 2-chloroethylphosphonic acid (Ethrel) thinned peaches. Applications at full bloom did not produce consistent thinning in ‘Cardinal’. Postbloom sprays applied approximately at endosperm cytokinesis produced consistent thinning of 3 cultivars.
Degree of thinning was related to time of Ethrel application. Most thinning was obtained when Ethrel was applied near the end of Stage I or during Stage II. Ethrel sprays within a month after full bloom caused significant fruit size reduction that persisted 2 months or more after treatment. Ethrel sprays within 50 days of harvest accelerated maturity of several cultivars.
Abstract
Postbloom application of gibberellin A3 (GA3) to open pollinated peach trees prevented seed development in some fruit, and also resulted in the persistence and maturation of both seeded and seedless fruit on the same trees. GA3 temporarily promoted fruit growth and delayed abscission of both seeded and seedless fruit, but the final crop load was not altered. Both seeded and seedless fruit abscised from treated trees during physiological drop. The persisting seedless fruit, therefore, competed successfully with seeded fruit. Seedlessness was associated with smaller fruit size at maturity.
Abstract
(2-Chlrorethyl)phosphonic acid (ethephon) advanced maturity of peach (Primus persica (L.) Batsch] by accelerating fruit development during me first 3 weeks of Stage III. Application early in Stage II did not affect fruit growth until the normal transition into Stage III, which indicates that ethylene does not initiate State III in the peach, but promotes fruit development once Stage III begins.
Abstract
Gibberellic acid (GA3) was applied at 75 ppm to mature ‘Redskin‘ peach trees at various times during the summer and fall. Flowering was reduced by GA3, the degree of reduction depending on time of application. Two response peaks were evident: the first occurred with application in early summer, at the time of flower initiation; the second occurred in late summer and resulted from mortality of developing flower buds. Application of GA3 shortly before leaf fall caused the most retardation of flower development the following spring. The nature and degree of flowering response was, therefore, related to time of GA3 application.
Abstract
Applications of potassium gibberellate (KGA) were made to ‘Redskin’ peach trees at various times after bud differentiation. KGA applied before leaf fall caused flower bud mortality and retarded bud development, depending on timing and concentration. Response peaks for each of these effects occurred at different stages in the development of flower buds. The KGA-induced retardation of floral development reduced the damage caused by frost during the bloom period. In contrast to the delay in bloom obtained when KGA was applied before leaf fall, flower bud development was accelerated when KGA was applied after a substantial part of the chilling requirement had been satisfied. The cold hardiness of the dormant flower buds was not greatly affected by KGA.