Anther wall development, placentation, sporogenesis and gametogenesis in Smilax davidiana A.DC: a contribution to the embryology of Smilax.
Embryological characters can be used to address taxonomic relationships and complement molecular phylogenetics and are of special value at the genus level. However, embryological information is fragmentary in Smilax and completely unknown in Smilax davidiana, a Chinese species. Anther wall development, placentation, sporogenesis and gametogenesis of S. davidiana are characterized here. The anther is bisporangiate, anther wall formation is of the Dicotyledonous type, both epidermis and endothecium develop fibrous thickenings, and the tapetum is secretory and of dual origin. Cytokinesis in the microsporocyte meiosis is successive, the microspore tetrad is tetragonal, and mature pollen is two-celled. The ovary is mostly trilocular with an axile placentation (a small fraction of the ovaries are unilocular with parietal placentation), the ovule is anatropous, bitegmic and crassinucellate, with embryo sac development of the Polygonum type. This study documents for the first time the embryological characters of S. davidiana in detail and contributes much to the embryology of Smilax.