喜树开花特性及繁育系统的研究

Flowering Characteristics and Breeding System in Camptotheca acuminata Decne

摘要:

定位观测了喜树(Camptotheca acuminata Decne)花部构造、开花特性, 用杂交指数(OCI)、花粉/胚珠比(P/O)、去雄、套袋、人工授粉等方法测定了喜树的繁育系统。结果表明：喜树花序为由4~6个头状花序组成的聚伞花序，聚伞花序上部的头状花序由两性花组成，下部的花序由雄花组成，两性花雌雄蕊发育正常，雄蕊10枚，雌蕊1枚，下位子房，一室，倒生胚珠；雄花雄蕊发育正常，雌蕊不发育。自然条件下，同一头状花序散粉后2 d，花粉活力最高；两性花在柱头外翻后3~4 d，柱头可受性最强，第6天失去可受性。喜树两性花为半同步雌雄蕊异熟类型，每个头状花序的所有小花同步开放，雄蕊先成熟，表现为雄性时期，雄蕊脱落后，雌蕊成熟，表现为雌性时期，上一级头状花序雌蕊成熟期与下一级头状花序雄蕊成熟期重合。繁育系统检测结果为部分自交和异交, 需要传粉者活动才能完成授粉过程。

Abstract:

The floral morphology and flowering characteristics in Camptotheca acuminata Decne were investigated. Breeding system was characterized by outcrossing index (OCI), pollen-ovule ratio (P/O), and the outcome of bag test and artificial pollination experiment. The results showed that the inflorescences of C. acuminata were cymes, each of which was composed of 4~6 capitula. Within a cyme, the 3~4 distal capitula were composed of hermaphroditic florets, while the 1~2 proximal capitula were composed of male florets. There were one pistil and ten stamens in each hermaphroditic floret. Each pistil possessed an inferior ovary containing an anatropous ovule. The male florets had normal stamens, but had no pistil. The pollen vigor in a capitulum reached its peak in the 2nd day after the pollen dispersal. The stigmatic receptivity reached its peak in 3rd and 4th days in the hermaphroditic florets. Stigma lost its receptivity completely on 6th day after it reflexed outward. C. acuminata was hemisynchronously dichogamous, and all florets of a capitulum bloomed synchronously. The male phase came first, in which the stamen matured. Then came the female phase, in which the pistil matured. The female phase of capitula in one order overlapped with the male phase of those in the next order in the same cyme. C. acuminata were outcrossing, partly self-compatible, and insect-assisted during the pollination.