The genesis of microspore and the formation of male gametophyte in Swertia davidii Franch

The present paper firstly reports the microsporogenesis and the formation of male gametophyte in Swertia davidii Franch..The main results showed that anther is tetrasporangiate.The development of anther walls conforms to the Basic type and comprises of epidermis, endothecium, three middle layers and tapetum at the mature stage. The tapetum cells have dual origin and belong to the glandular type. The degenerating tapetum nuclei in the middle of anther locules are from the tapetum cells, which undergo mitosis, then intrude into the anther locules and degenerate in situ at the early stage. Three middle layers are ephemeral. Endothecium degenerates shortly after differentiating; epidermis persists and develops to become histogram elongated and fibrous-thickening. The cytokinesis of the microspore mother cells in meiosis is of the Simultaneous type. Most of the microspore tetrads are tetrahedral and there are still a few other types, such as isobilateral, dilateral and “T”-shaped. Pollen grains are 2-celled when shed.