茨藻科、角果藻科植物花粉形态的研究

在水生植物茨藻目中，茨藻科Najadaceae和角果藻科Zannichelliaceae植物由于其结构、尤其是花部结构的极度简化和趋同适应，系统关系仍不清楚。本文应用光学显微镜、扫描电镜和透射电镜对上述2科4属的10种代表植物的花粉形态进行了观察，系统描述了各属、种的花粉形态。结果表明角果藻科植物花粉均无萌发孔，外壁纹饰通常为拟网状至浅网状。花粉形态的研究结果支持将Vleisia作为角果藻属Zannichellia的近缘属处理的观点。茨藻科植物花粉外壁光滑、稍皱波状或为疣状，具颗粒状纹饰，萌发孔的有无在种间存在变异。花粉形态的研究结果表明角果藻科与眼子菜科Potamogetonaceae近缘，茨藻科可能与水蕹科Aponogetonaceae或水鳖科Hydrocharitaceae中具单沟花粉的类群有一定联系，而与角果藻科和眼子菜科则相去甚远。

Pollen morphology of Najadaceae and Zannichelliaceae

WT5BZ]In the aquatic order Najadales, severe structural reduction, particularly the floral structure reduction, and strong convergence of morphological characters occurring in the Najadaceae and Zannichelliaceae have greatly obscured their phylogenetic relationships and presented systematists with difficult problems in understanding their phylogenetics. To gather more basic phylogenetic information regarding Najadaceae and Zannichelliaceae, pollen morphology of 4 genera of these two families was examined with light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Our results provide the following insights: (1) Pollen grains of Zannichelliaceae are inaperturate, subspheroidal or subprolate, with ornate or reticulate exine sculpturing. Pollen grains of Vleisia and Zannichellia are smaller, usually with ornate sculpturing, while those of Lepilaena are larger, with crispate, ornate or reticulate sculpturing. (2) Pollen grains of some species, e.g. Najas oguraensis Miki and N. flexilis (Willd.)Rostk. et Schmidt. in Najadaceae, are monosulcate, but in some other species studied here they are inaperturate. Pollen grains of this family usually have not exine sculpturing, but those of N. oguraensis Miki and N. flexilis (Willd.)Rostk et Schmidt have verrucate or granular sculpturing. (3) Evidence from the aperture, wall sculpturing and structure of pollen grains does not support the viewpoint that Najadaceae is closely related to Zannichelliaceae and Potamogetonaceae, but shows that Zannichelliaceae and Potamogetonaceae are near relatives.