Seed coat morphology of Smilacaceae and its systematic significance
1,2CHEN Shi-Chao 2SEINE Nyoe Nyoe Ko 2FU Cheng-Xin* 1(College of Life Science and Technology, Tongji University, Shanghai 200092, China) 2(Laboratory of Systematic and Evolutionary Botany and Biodiversity, College of Life Sciences, Zhejiang University, Hangzhou 310058, China)
Macromorphology of seeds and micromorphology of the seed-coat in 53 species and 5 varieties belonging to three genera (Smilax, Heterosmilax and Ripogonum) of Smilacaceae were observed under the light microscope and the scanning electron microscope (SEM). The seeds are spheroidal, hemispheroidal or trigonal-oblate in shape. Under SEM high diversity was found in seed-coat micromorphology. Based on ornamentation of epidermal cells of the seed-coat, seven morphological types can be distinguished, viz., roughly rugulate, rugulate, reticulate, fine reticulate, foveolate, dense foveolate, and fine striate. Discriptions of seed size, shape and seed-coat types are summarized for the family. Taxonomic and phylogenetic implications of the seed-coat micromorphology are also discussed, in relation to the circumscription of traditional genera and sections of the family. Evidence from seed-coat micromorphological features supports placement of Ripogonum outside Smilacaceae and inclusion of Heterosmilax in Smilax, which are also consistent with palynological and molecular evidence. Within Smilax, seed-coat micromorphological features suggest close relationships between most of the species of sect. China and sect. Macranthae, and among sect. Coprosmanthus, sect. Coilanthus, and Heterosmilax. However, we found no support for the recognition of Koyama’s six proposed sections of Smilax.