DORMANCY IN PEACH (PRUNUS-PERSICA L) FLOWER BUDS .4. MORPHOGENESIS OF EXCISED BUDS AS INFLUENCED BY CHILLING AND GIBBERELLIN A(3)

Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2-4 degrees C for 30 days) and unchilled buds were exposed to 20 to 25 degrees C, 100% RH and continuous light. Gibberellin A(3) (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin Ag applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A(1/3) we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development.