Leaf epidermal features of Chinese Stephania Lour. (Menispermaceae) and their systematic significance
A previously published molecular phylogeny of Chinese species of Stephania (Menispermaceae) showed that none of the sections sensu Luo, recognised based on flower, inflorescence, leaf, and tuber traits, was monophyletic. In order to assess the use of an additional vegetative character for supraspecific classification in Stephania, we conducted an analysis of leaf micromorphology. Leaf epidermal features of 34 out of the c. 40 Chinese species of Stephania were investigated using light and scanning electron microscopy. Leaf epidermal characters were found to be constant at species level, but variable among species. The distribution pattern of papillae on the epidermal cells of the adaxial and abaxial sides of the leaves revealed three groups in Stephania, fitting with the recognition of three subgenera. Combined with the latter character, the shape of anticlinal cell walls proved to be useful to discriminate between sections, at least in subgenus Stephania. In addition, our results show that S. chingtungensis (subg. Stephania) exhibits leaf micromorphological states characteristic of subgenus Tuberiphania. The systematic position of the recently described S. novenanthera and of the taxonomically challenging S. excentrica within subgenus Tuberiphania is suggested by leaf epidermal features.