百香果開花習性之研究

On the Flowering Habit s of Passionfruits

本文以「臺農1號」品種之百香果為主要材料，探討其開花習性等相關研究。百香果之花芽從新梢的葉腋中產生，花芽著生在卷鬚旁側，從實地調查，組織切片及SEM觀察結果判斷百香果之卷鬚和花芽應屬同源器官。推測其發育過程為：首先自葉原體腋中形成一芽體，稱為卷鬚──花芽原體tendril-Flower primordium，此芽體稍大時均分為二，靠近葉原體部份形成卷鬚，另一部份則形成花芽。在卷鬚──花芽原體分化的同時，其內側（近軸面）另形成一營養芽。可見百香果之花芽和營養芽在一開始即已分開。百香果之實生苗表現幼年性，葉片全緣不分裂，而且幼年葉葉腋並不形成卷鬚──花芽原體，而只形成營養芽，因此幼年期植株不形成卷鬚和花芽，自然也不具開花能力。扦插（或嫁接）苗在基部數節亦不形成卷鬚和花芽，呈再幼年化（rejuvenlation）現象。似乎實生苗及扦插（或嫁接）苗均在其特定節位以上開始形成花原體（亦即花芽始發），因此推斷百香果屬於自我誘導植物（autonomous induction）。然而花原體形成並不保證能順利開花，而必須達到開花成熟度以及有利環境之配合才能達成。因此花芽發育（尤其是花器形成）才是決定百香果開花與否之重要關鍵。

The flowering habits of passionfruit, especially cv. Tai-nung No. 1 (Passiflora edulis × P. edulis f. flavicarpa) were evaluated. The flower buds arc borne singly in the leaf axils of new growth, and each flower bud at the side of the tendril. Observations by histochemical sections, and scanning electron micrographs, we suggest that the tendril and the flower bud are homologized organs. The developmental process is interpreted that an axillary bud (i.e. tendril-flower primordium) arises from the axil of young leaf primordium and then divides dichotomously, one tip which closer leaf primordium developing into the tendril primordium and the other into the flower primordium. Meanwhile a vegetative bud adjacent to the axis occurs. So the flower bud is separate from the vegetative bud at the beginning. Seedlings of passionfruit express characters of juvenility, that is ovate leaves and no tendril-flower primordium in the axil of juvenile leaves. So neither tendril nor flower bud occurs in juvenile plants which have no flower ability. The lower nodes of cuttings or grafted plants express similar characters of juvenile plants, that is rejuvenation. It seems that either seedlings, cuttings or grafted plants form the first flower primordium at their special node. So we suggest passionfruit is a plant of autonomous induction. However, the flower primordia at the lower nodes usually can't form flower buds and flower until the plants reach the condition of flowering maturity and meet the suitable environment. Therefore the flower development, especially the stage of flower, organization, is the key factor to determine whether flower or not.