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

Morphological studies were carried out with peach flower buds collecte d 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 degr ees 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 sampl ed and processed for histological studies. Cultured flower buds (chill ed or unchilled) had accelerated anther and gynoecium morphogenesis af ter 12 days under controlled conditions, compared to buds processed im mediately after collection from the field. Chilling treatment augmente d the bud culture effect, while Gibberellin Ag applications to the exc ised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the compar atively high levels of Gibberellin A(1/3) we previously found in mid w inter [15, 18] could be at least one of the factors that controls flor al bud dormancy by retarding anther and gynoecium development.