中国水鳖科植物种皮微形态特征及其系统学意义

通过扫描电镜对国产水鳖科植物(包括6属13种)的种皮微形态特征进行观察，并作了系统描述。根据种皮细胞形态、外种皮表面纹饰和内种皮内层小瘤状突起的特点将水鳖科植物的种皮微形态特征划分为3种类型，即海菜花型(海菜花属)、水鳖型(水鳖属)和苦草型(苦草属、水筛属、虾子草属和黑藻属)，并作出了分属检索表。本文结果表明，种皮微形态特征可作为该科族、属以及属内种级水平分类的依据，对探讨属间关系和该科的系统发育关系亦具有重要的价值。种皮微形态特征支持Hutchinson(1959)和Eckhardt(1964)将海菜花属和水鳖属分别作为一个独立的族处理的观点。苦草属、水筛属和虾子草属种皮微形态特征的高度相似性表明它们间有密切的联系，不支持将它们置于不同亚科和族的分类处理。黑藻属虽与上述3属近缘，但其外种皮特征则较为独特，因此与水筛属放在不同族中更为合理。本文种皮微形态特征的研究结果支持iki1937)和Shaffer-Fehre(1991b)等关于水鳖科与茨藻科近缘的观点。

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

The importance of characters of seed coat for taxonomic and systematic research has begun to be appreciated in studies on the subclass Alismatidae recently. The present study examined micromorphological characters of seed coat of six genera, including 13 species, in the Hydrocharitaceae from China under scanning electron microscope. The characters are described and three types of seed coat are distinguished here according to cell shape of exotesta and endotegmen, sculpture of seed surface and endotegmen tuberculae: (1) Ot-telia type, of which the seed coat sculpture is absent, ridged or pilose, cell of endotegmen is polygonal to nearly oblong, and tuberculae sparsely are granulate (e.g. Ottelia Pers. ) ; (2) Hydrocharis type, of which the seed coat sculpture is verrucate, cell of endotegmen is irregular, and tuberculae densely are baculate (e.g. Hydrocharis L.); (3) Vallisneria type, of which the seed coat sculpture is verrucate, cell of endotegmen is oblong or nearly oblong, and tuberculae densely are tuberculate (e.g. Vallisneria L., Blyxa Thou et Rich., Nechaman-dra Planch., Hydrilla Rich. ) . There are some differences between genera as well as species in characters such as cell shape of seed coat, sculpture of seed surface and endotegmen tuberculae, and these characters can be served as diagnostic ones for distinguishing tribes, genera and even species in this family. Micromorphology of seed coats supports Hutchinson's (1959) and Eckhardt's (1964) treatments about the tribes Ottelieae and Hydrochariteae. Vallisneria L., Blyxa Thou et Rich., and Nechamandra Planch, should be placed in the same tribe, and the genus Hydrilla Rich, is closely related to them. In addition, the similarity of verrucae on the seed surface as well as endotegmen tuberculae between the Hydrocharitaceae and Najadaceae may indicate that the two families are closely related.