Anther and ovule development in Clematis terniflora var. mandshurica (Ranunculaceae)

Abstract

Embryology can provide valuable information for determining taxonomic and phylogenetic relationships at the genus level. However, embryological information is fragmentary for the genus of Clematis. Herein, we studied the anther and ovule development of Clematis terniflora var. mandshurica using paraffin sections to examine microsporogenesis, microgametogenesis, megasporogenesis and macrogametogenesis in this plant. Tetrasporangiate anther, successive microsporocyte cytokinesis, and glandular tapetum, or occasionally amoeboid tapetum were observed in C. terniflora var. mandshurica. This plant’s microspore tetrads were mostly tetrahedral, and occasionally symmetrical, after meiosis. The anther wall was comprised of an epidermis and endothecium, both with fibrous thickenings in the mature anthers. Pollen grains were symmetrical, oblate, tricolpate, and two-celled. As for the ovary, it had one chamber with a few degraded ovules and a single normal one, which was anatropous, unitegmic, and tenuinucellate, and formed a Polygonum-type embryo-sac. Only one archesporial cell was present, and developed directly into a megaspore mother cell, which later formed a linear tetrad of megaspores. Larger dikaryocytic antipodal cells could also be observed in the mature embryo sac. This species might belong to a relatively primitive and transitional clade within the genus Clematis. To our knowledge, this study documented the embryological characters of C. terniflora var. mandshurica in detail for the first time and provided more information on the embryology of the genus Clematis.