| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 88 === We studied how the endogenous and exogenous cytokinin and gibberellin functions in floral
initiation and development in tuberose. In the aspect of cytokinins. The contents of endogenous
cytokinin in tuberose corms (Polianthes tuberosa L. cv. Double) at vegetative, early floral
initiation, and flower development stages were investigated. We also determined the influence of
exogenous cytokinin treatment on the corm apex at three different growth stages in relation to
floral initiation and development in tuberose. The exogenous cytokinin effectively induced
floral initiation and development, especially at the early floral initiation and flower
development stages. Endogenous cytokinins were higher in early floral initiation and development
stages in comparison to the vegetative stage. During floral initiation stage, the zeatin and
dihydrozeatin increased significantly, while the cytokinins, zeatin riboside, dihydrozeatin
riboside, 6N-(δ2-isopentenyl) adenine, and 6N-(δ2-isope -ntenyl) adenine riboside at consistently
low levels. The increase of cytokinin levels in tuberose corms during floral induction suggests a
role for cytokinins in tuberose apex evocation. Moreover, these results indicate that cytokinins
seem to promote the development of flower buds rather than inducing flowering in tuberose.
Endogenous gibberellins (GAs) in tuberose corms were isolated using high performance liquid
chromatography, bioassay and identified by combined capillary gas chromatography-mass
spectrumetry. Gibber -ellins A19, A20 and A53 were quantified at the vegetative, early floral
initiation and flower differentiation stages. The identification of these 13-hydroxylated GAs
indicates the presence of the early-13-hydroxy -lation in tuberose corms. An increase in GA20 and
decrease in GA19 coincided with the transition from the vegetative phase to the stages of early
floral initiation and flower differentiation. GA53 maintained at constant levels at three
different growth stages. When GA3, GA4, GA20 and GA32 were applied to corms at vegetative stage
(plants about 5 cm in height ), floral initiation was induced and/or promoted by several, most
notably by GA3, GA20 and GA32. It is suggest that hydroxylated C-19 GAs play an important role in
flower induction in tuberose.
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