番木瓜兩性株花器形成過程之形態觀察

Morphological Examination of Floral Oragnization in Hermaphroditic Papaya (Carica Papaya L.)

台農二號番木瓜兩性株各齡花芽以解剖顯微鏡及掃描式電子顯微鏡（SEM）觀察。其花器形成過程依形態觀察可分為萼片及花瓣原基相繼出現的花被原形成期（第1-3節），雄蕊及心皮原基相繼開始形成的雌雄花器原墓初形成期（第4-6節），花藥與花絲明顯可見的雄蕊形成完整期（第7-9節），以及心皮完全癒合且形成分支狀柱頭的雌蕊形成完整期（第10-14節）。花器形成之進程與其所著生之節數有穩定之關係故可透過節位標定的方法來推測芽體的發育程度。番木瓜之花器形成為向頂的（acropetal）分化模式，以SEM觀察第5-8節腋花序軸頂花雌雄花器原體形態，可清楚地看出其變化。第l節可視為花器形成之始，而第14節則可視為花器形成完整之時期，其中雄蕊之形成在第4-9節而雌蕊在第6-14節。花器形成所需時間會依季節不同在4-10週間變動；而花器成熟所需時間則較恆定，約3-5週。在雄蕊形成期間不同階段發生之雄蕊心皮化現象會造成不同程度之畸形花型，而於雌蕊形成期間不同階段發生之發育受阻現象，則會形成不同心皮數及柱頭數的雌蕊。本研究之結果所找出各種花型在形態上之決定時機，與前人所推測環境因子影響雌雄蕊發育之關鍵時期有約2-3節之差異。

Floral buds of hermaphroditic papaya cv. ”Tai-Nong No.2” were examined under stereomicroscope and scanning electron microscope. According to morphological characters, the processes of floral organization were divided to four stages: a) perianth primordia formation stage in which sepal primordia appear followed by sepal primordia do; b) sexual organ primordia initiation stage in which stamen and carpel primordia initiate subsequently; c) complete stamen organization stage in which anthers and filaments can be recognized easily; and d) complete gynoecium organization stage in which the connection of carpels is finished while the branched stigmas were observed. The pattern of floral organization of papaya like most plant species, was acropetal in the order of floral organ occurrence. The degree of floral organization of apical bud in a inflorescence depended on the order of the node on which the inflorescence subtended. Therefore through the reliable labeling method of this study, nondestructive estimation of condition of the floral bad was possible. Floral organization began at node no. 1 and finished at node no. 14. Stamen organization was from node no. 4 to node no. 9 white pistil organization was from node no. 6 to node no. 14. The duration of floral organization fluctuates 4-10 weeks due to seasonal variation, but the floral maturation was constant, it was needed 3-5 weeks no matter of season change. Carpelloid occurring in various stages of stamen organization resulted in various kinds of teratologic flowers, while abortion of carpets occurring in various stages results in pistil with various number of carpels and stigmas. The morphological determination point of various flower types surmised in this study is 2-3 node later than the period that environmental factors could effect floral organization. Further physiological and molecular biological studies of this period will be needed in constructing the mechanism of papaya floral variation.