中国茨藻科植物种皮微形态特征及其系统学意义

本文应用扫描电镜对国产茨藻科植物的外种皮和内种皮微形态特征进行了研究，结果表明茨藻科植物在种子表面细胞形态、表面纹饰和内种皮内层细胞形态及小瘤状突起的大小和密度等方面存在差异，可作为种级水平分类的依据，并首次发现外种皮微形态特征也与内种皮内层小瘤状突起一样具有重要的系统学意义。根据种皮微形态特征的研究结果，我们支持Miki(1937)和Shaffer-Fehre(1991b)等关于茨藻科与水鳖科近缘，而不应放在眼子菜目的观点。对弯果茨藻Najas ancistrocarpa A．Br．ex Magnus和草茨藻N.graminea Del.外种皮的研究结果表明其外种皮细胞表面具瘤状颗粒而非网状加厚。

MICROMORPHOLOGICAL CHARACTERS OF SEED COATS OF CHINESE NAJADACEAE AND THEIR SYSTEMATIC SIGNIFICANCE

; The Najadaceae is one of families of the subclass Alismatidae. Although the systematic value of characters of seed coats has been appreciated in this family, further micro-morphological study of seed coats is still essential to Chinese species. The present authors examined the micromorphological characters of seed coats of the Najadaceae from China using scanning electron microscope. The details about micromorphological characters of seed coats of six species are given here. The results show that the external tangential walls of exotesta are covered with filamentous stripes or dense verrucae. The latter only exist in Najas an-cistrocarpa and N. graminea . The cell of endotegmen is usually narrowly oblong, and en-dotegmen tuberculae on the internal tangential walls are found in all the six species studied, which is identical with the report of Shaffer-Fehre (1991a) for other species in this family. These characters are useful for taxonomic research at specific level. It is found for the first time that just like endotegmen tubercula, the sculpture patterns on the surface of seed coat, such as filamentous stripes and verrucae, are similar to those of the Hydrocharitaceae, indicating that they have important value for systematics of the Najadaceae. The evidence from seed coat supports the viewpoint of Miki(1937) and Shaffer-Fehre (1991b) that the Najadaceae is closly related to the Hydrocharitaceae and should not be treated under the order Potamogetonales.