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Studies of exogenous hormone application to apple in relation to flowering, fruit set, and fruit quality
Abstract
Experiments were initiated to determine if calcium (Ca) acted as a 'second messenger' mediating hormone response in apple. Benzyladenine (BA) and gibberellins GA$\sb4$ or GA$\sb{4/7}$ were applied alone or in combination with either verapamil or trifluoperazine, as a foliar spray or by injection into the calyx end of 'Delicious' around two weeks after full bloom. There were few gibberellin and Ca modifier interactions. It is concluded that if Ca is acting as a 'second messenger' in mediating hormone response, its contribution is peripheral at best. Experiments were conducted to examine the relationship between flowering and fruit set in apple and endogenous levels of polyamines in developing fruit and leaves. Cytokinin (BA), gibberellins (GA$\sb4$, GA$\sb7$, GA$\sb{4/7}$) and 92 percent shade were used to modify flowering and fruit set. In addition, in experiments with 'Cortland' and 'Idared', differences between fruit on the same cluster were evaluated. In general, polyamines within the developing fruit decreased with fruit development. Spermidine was the predominant polyamine, followed by putrescine and then spermine. Small fruit in a cluster generally contained higher levels of polyamines than large or abscising fruit. No relationship was found between endogenous polyamines and flower bud initiation. In 'Cortland', 'Golden Delicious', and 'Idared', peaks occurred in putrescine and spermine content in developing fruit just prior to abscission peaks associated with 'June drop'. A cyclic pattern of putrescine in small 'Idared' fruit may be related to natural abscission waves in apple. Putrescine and spermidine levels in 'Idared' leaves were reduced with a 92 percent shade treatment. Two experiments were initiated to examine the relationship between exogenous hormone application and exogenous levels of cytokinins in developing apple leaves. A foliar application of BA produced a 48-fold increase in trans-zeatin riboside-like activity in developing leaves.
Subject Area
Plant sciences
Recommended Citation
Cohen, Robin Alice, "Studies of exogenous hormone application to apple in relation to flowering, fruit set, and fruit quality" (1991). Doctoral Dissertations Available from Proquest. AAI9120863.
https://scholarworks.umass.edu/dissertations/AAI9120863