| Summary: | 碩士 === 國立臺灣大學 === 園藝暨景觀學系 === 105 === Pitaya (Hylocereus sp.) is a typical long-day plant with critical day length about 12 hours, and its floral initiation may complete around eight weeks after spring equinox. CPPU may interfere with the balance between cytokinin and auxin in the meristem and thus promote bud emerging at instant differentiating status instead of completeing floral initiation. The objective of this research was to build the basic information of pitaya floral initiation via spraying 100 mg·L-1 CPPU solution on current shoots that sprouted at different timing.
Mature current shoots, grew more than 15.5 weeks before spring equinox, were competent to response to long daylength at spring equinox. After 7.5 weeks of the long daylength induction, the mature shoots completed floral initiation and emerged typical flower buds. The bud emergence of immature shoots was much late due to the incompetent of responsing to long daylength induction at spring equinox. Therefore, applying CPPU on 7.5 weeks after spring equinox, matured shoots were able to emerged typical florsl bud and immature shoots emerged abundance of partial evocation flower buds insteds of typical floral buds.
In our study, the inductive daylength was predicted more presicesd, ranging between 11 hours 53 minutes and 12 hours 2 minutes, for pitaya floral initiation was onset 1.5 weeks before spring equinox. The duration of pitaya floral initiation required 9 weeks, with 5 weeks of induction and 4 weeks of evocation, and earlist floral bud emergence was recorded on 19 May 2017, which was 8.5 weeks after spring equinox. In the process of floral initiation, pitaya buds should transit from vegetative phase to reproductive phase. Upon the transition, the morphological changes of bract formation phyllotaxy alteration, and floral primordia formation should be completed. Interrupting the transition by CPPU, the emerged buds expressed sequential changes relative to long daylength duration that the shoot received.
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