AN ABSTRACT OF THE THESIS OF Carlos H. Crisosto for the degree of Doctor of Philosophy in Horticulture presented on November 18. 1987 Title: The Effect of Ethylene Manipulation on Flower Bud Development

Abstract approved: , .. In the Northwest, two tree fruit production problems may be related to the role of ethylene on plant growth and development: flowers and developing fruits are subject to low temperature injury during early spring, and to the low fruit set of 'Cornice'. Ethylene may be involved in influencing dormancy and flower and ovule senescence. Thus, manipulation of the ethylene levels during various stages of development may alleviate these problems. The role of ethylene on floral bud break was studied by the appli-cations of ethylene inhibitors and ethephon, an ethylene generator, during various stages of floral bud development. Lower concentrations of a fall ethephon spray at the onset of dormancy delayed subsequent anthesis by 8 and 13 days on peach and prune fruit trees without exces-sive damage. This ethephon spray was associated with high levels of internal bud ethylene and ABA. The slower in the rate of flowe