驴蹄草属和金莲花属(毛茛科)花器官的形态发生及系统学意义

利用扫描电镜观察了驴蹄草Caltha palustris L.和川陕金莲花Trollius buddae Schipcz.花器官的发生和发育过程。结果显示:驴蹄草和川陕金莲花的所有花器官均螺旋状向心式发生、向心式发育,花器官的螺旋状发生方式在毛茛科Ranunculaceae可能是一种基本式样;苞片、萼片与其他花器官原基的形状明显不同,显示苞片、萼片与其他花器官在系统发生上有所不同;川陕金莲花的花瓣在早期延迟发育且基部具囊,花瓣的延迟发育在毛茛科具花瓣的属中非常普遍,而花瓣基部的囊类似于耧斗菜属Aquilegia一些植物;两个属雄蕊群一纵列雄蕊中的小孢子均向心式发育,这种发育方式在毛茛科可能为基本类型。两个属植物的心皮原基均为对折式,在发育过程中,驴蹄草心皮顶端沿腹缝线形成下延的柱头组织,川陕金莲花不形成明显的柱头组织。根据花形态发生和发育特点,并结合其他研究成果,认为这两个属不应当属于同一个族。

Floral morphogenesis of Caltha and Trollius (Ranunculaceae) and its systematic significance

The floral morphogenesis of Caltha palustris L. and Trollius buddae Schipcz. was observed with a scanning electron microscope (SEM). The primordia of all floral organs initiate spirally and centripetally and develop centripetally. The spiral initiation sequence may be a basic pattern in Ranunculaceae. The primordia of bracts, sepals, and other floral organs are different in shape: the bract primordia are triangle, the sepal primordia crescent, and the petal (in Trollius), stamen, and carpel primordia hemispheric. This may indicate that the bracts, the sepals and other floral organs are different in origin. The petals are retarded in early developmental stages in Trollius buddae Schipcz, and have purses at the base. The retarded petals are very common in Ranunculaceae and the purse of the petal is similar to that of some Aquilegia species. The microspores in a longitudinal series of stamens develop centripetally in Caltha and Trollius; this may be a basic pattern in Ranunculaceae. The carpel primordia are plicate. In the developmental process of the carpels, the stigmatic tissue appears from the apex of the style and is decurrent along the ventral suture in Caltha, but there is no obvious stigmatic tissue in Trollius. Based on floral morphogenesis characteristics as well as the results from molecular systematics, comparative morphology and palynology studies, we consider that Caltha is not closely related to Trollius and that these two genera should not be treated in the same tribe.