Floral Organogenesis Of Brasenia, Nymphaea And Euryale And Its Systematic Significance

In order to analyze the systematic relationships among the three genera: Brasenia, Nymphaea and Euryale, the floral organogenesis of their representatives has been studied by SEM. The results are as below: 1. In Brasenia, 3 sepal primordia and 3 petal primordia initiated stimultaneously in each whorl. The first six stamen primordial initiated in a whorl stimultaneously, and the succeedings ones initiated in irregular spirals. Ascidiate carpel numerous, initiated in spirals. In Nymphaea, 4 sepal primordia initiated from abaxial to adaxial side of the floral apex. Petal and stamen numerous, initiated in spirals. The apex of floral primordium caved in at the late stage. Plicate carpel 6~8, initiated in a whorl stimultaneously. Euryale' s floral organogenesis is similar to Nymphaea' s except the apex of Euryale' s floral primordium caved in at early stage. The study of floral organogenesis of these three genera enriched the systematic data of Nymphaeaceae (s. 1.), and would be very valuable to the analysis of systematic relationships among these three genera and the members in Nymhphaeaceae, even in Nymphaeales.2. Brasenia quite differs from Nymphaea in floral organogenesis, so it shouldn' t be treated in the same family with Nymphaea, and should be separated from Nymphaeaceae. It has more primordial characters than Nymphaeahas, so it should has a more primordial status than Nyphaea' s.3. Euryale is very similar to Nymphaea in floral organogenesis, so it should be treated in the Nymphaeacea together with Nyphaea. Considering the difference of the shape change of their floral primordium apex etc, Euryale should be more evolutional than Nymphaea, and it shoud be an evolutional group in Nymphaeaceae.4. Although these three genera have some differences in floral organogenesis, they have some common primordial characters, such as have spiral initiation mode and numerous stamen primordial etc. So they should be the primordial groups of angiosperm.