突脉金丝桃的花器官发生及其系统学意义

利用扫描电镜（SEM）观察了突脉金丝桃（Hypericum przewalskii）（金丝桃科）的花部器官发生发育过程。结果表明，突脉金丝桃2枚苞片原基首先发生，花原基在苞片原基的包裹中完成发育。在苞片原基发生后，5枚萼片原基沿2/5圆周依次发生。萼片原基发生近完成时，5枚雄蕊—花瓣共同原基在萼片原基之间的角隅处近同时发生，此后，雄蕊—花瓣共同原基下部向外伸展形成花瓣原基，上部向上凸起形成与花瓣原基相对的雄蕊原基，之后雄蕊原基由内向外依次分化发育产生次生雄蕊原基，随着次生雄蕊原基的发育和数目的增多，形成了5束雄蕊。次生雄蕊原基发生的同时，5枚心皮原基近同时发生。突脉金丝桃雄蕊束的发生方式表明，金丝桃属的雄蕊束可能起源于5基数的单轮雄蕊。金丝桃科与藤黄科植物花瓣及雄蕊原基发生方式的显著不同，支持了APG Ⅲ系统将金丝桃亚科从藤黄科中独立为金丝桃科的观点。

Floral Organogenesis of Hypericum przewalskii(Hypericaceae) and Its Systematic Implications

The floral organogenesis of Hypericum przewalskii（Hypericaceae） was observed under scanning electron microscope. Two bract primordia occur first， and the flower primordium develops in the package of the bract primordia. Followed the initiation of bract primordia， five sepals are initiated by 2/5 circumference spiral. With the sepal primordia initiated， the angles between the sepal interstices swell up into large protuberances which become differentiated as common stamen-petal primordia. Five common stamen-petal primordia initiated simultaneously. Petal primordia are separated from the lower half of the common stamen-petal primordia by a median slit. The remaining upper half of the common stamen-petal primordia grows into a hemispherical structure， thus the five stamen primordia initiate opposite to the petal primordia. Then the stamen primordia sequentially differentiated from the inside to the outside to produce the secondary stamen primordia. With the development of the secondary stamen primordia and increasement of primordia， fascicled stamens were formed. When the secondary stamen primordia initiated， the five carpal primordia initiated in a simultaneous type. The development way of the fascicled stamens in H.przewalskii indicated that fascicled stamens in Hypericum may originate from haplostemonous structure. The significant difference in patterns of petal and stamen primordia between Hypericaceae and Clusiaceae supports the viewpoint of APG Ⅲ classification that Hypericaceae are separated from Clusiaceae.