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基部被子植物金粟兰科(Chloranthaceae)的单性花或两性花结构十分简单,雪香兰(Hedyosmum orientale)花单性、雌雄异株,花的形态及结构与其它属物种具有显著的差异,对于研究被子植物花特别是花被的起源和系统进化具有重要意义。该研究采用电子显微镜和光学显微镜观察了雪香兰单性花的器官发生及发育过程。结果表明,雌、雄花均为顶生和腋生,多个小花呈聚伞圆锥状排列。雄花外侧是苞片,每朵雄花上着生150–200个雄蕊,花轴基部着生少数退化的叶原体。苞片原基及其腋生的花原基最初呈圆丘状,随后伸长。在雄花发育过程中,苞片原基比雄蕊原基生长快,雄花原基纵向伸长,叶原体原基在基部发生,雄蕊原基自下而上发生。每2朵雌花底部合生形成小聚伞花序,每朵雌花被一苞叶包裹,由单心皮和三棱型子房构成,外覆三裂叶状花被。在雌花发育过程中,雌花原基比苞片原基生长快,花被原基首先于花顶端发生,随后花顶端中心凹陷,进一步发育成具有单心皮的子房原基。雪香兰的单性花发育不经过两性同体阶段,花分生组织只起始雄蕊器官或雌蕊器官的发育。研究结果支持雪香兰单性花是原始性状的观点,雄花叶原体与雌花三裂叶状花被同源,可能是花被(萼片与花瓣)的起源。
The unisexual or bisexual flower structure of Chloranthaceae is very simple. The flowers of Hedyosmum orientale are unisexual, dioecious, the morphological and structural features of flowers are significantly different from those of other genera. The angiosperm flowers, especially the origin and phylogeny of perianth, are of great importance. In this study, the organogenesis and development of unisexual flower of Xueyelan were observed by electron microscope and optical microscope. The results showed that both female and male flowers were terminal and axillary, and many florets were arranged in a parachute cone. Male flowers lateral bracts, each male flowers on the stamens 150-200 stamens, flower axis base with a small number of degraded leaf primordia. Bracts primordia and their axillary primordia initially dome-shaped, followed by elongation. During male flower development, bracts primordia grow faster than stamen primordia, longitudinal elongation of male flowers primordia, primordia of leaf primordia occur at base, and stamens primordia occur bottom-up. Each 2 flower female connate at the bottom of the formation of cymules, each flower is a bract leaves wrapped by the single carpels and triangular-shaped ovary, covered with three-tipped leaf-shaped perianth. In the process of female flower development, the female flower primordium grows faster than the bract primordia, the primordium of perianth first occurs on the flower tip, and then the flower apical center is depressed to further develop into a primordial base with ovary. Xueyelan unisexual flower development does not go through the stage of both sexes, flower meristem tissue only start the development of stamens or pistil organs. The findings support the view that the unisexual flower of Xueyelan is a primitive trait. The male flower mosaic is homologous to the leaflike flower of the female flower, which may be the origin of the perianth (sepals and petals).