三白草科花部发育及其系统学意义

本研究从比较三白草科属间小花个体发育及分析花器官数量变异入手,探寻花器官在发生顺序、数目变化及排列方式等方面的演化趋势,揭示系统发育在个体发育中一定程度重现的事实及属间的进化关系。结果简述如下:首先,雄蕊和心皮发生顺序由中部优先演化到两侧优先。其次,由于远中雄蕊和心皮经历了从发育延迟、生长减缓到最终消失的历程,中部雄蕊和心皮由成对演化为单生。此外,两侧生雄蕊对由各自独立的原基发生演化到共同原基发生或减化为1枚,假银莲花属近中1枚雄蕊原基二裂成1对,蕺菜属3枚心皮发生于一环状共同原基等,都是该科花器官演化的重要事实并可归结为融合、减化和复化的结果。文章根据花器官的演化趋势及过渡类型的剖析,论述了三白草科属间的系统进化关系。

ON THE SYSTEMATIC SIGNIFICANCE OF FLORAL ORGANOGENESIS IN SAURURACEAE

The sequence of organ initiation and the change in number and position of stamens and carpels are compared among the four genera in the Saururaceae in this paper. Several evolutionary trends of organogenesis are revealed and summarized as follows; The first trend is that the first appearance of stamens and carpels converts from the median sagittal ones to the lateral ones. In Saururus the median sagittal stamens and carpels all appear first, while in Gymnotheca the median posterior stamen arises first, the lateral pair second, the median anterior one third, and the lateral carpels appear first. In Anemopsis and Houttuynia the lateral stamens have changed to arising first. The second trend is the conversion of initiation of stamens and carpels from the median sagittal ones in pair as in Saururus to singular, acompanied by delayed development in Gymnotheca and to final degeneration of the anterior stamen and carpel in Anemopsis and Houttuynia. The latter two genera have a pair or only one stamen at the posterior position, but during early development there is a gap as a trace of degenerating stamen at the anterior position. Moreover, in Gymnotheca with four carpels, a gap exists at the anterior position, which is the place of the delayed anterior carpel; in the genera with three carpels, a gap is present at the anterior position in Anemopsis , but absent in Houttuynia. The other trends involve the change of the two lateral stamens from separate initiation in Saururus to initiation from a common primordium in Gymnotheca and Anemopsis and to reduction of one stamen in Houttuynia; the conversion of single posterior stamen to a pair from a common primordium in Anemopsis; the change of initiation of three carpels from separate primordia in Anemopsis to from a ring primordium in Houttuyni-a. The facts seem to show that the genus Houttuynia is more advansed than Anemopsis. The evolutionary trends of flowers in the Saururaceae can be expianed as the results of fusion, reduction and multiplication. The systeraatic relationships among the four genera were inferred in a diagram.