The Formation Of Microspore And Megaspore, Development Of Male And Female Gametophytes And Fertilization In Dioscorea Zingiberensis

Different Dioscorea zingiberensis C.H. Wight populations were used as materials in this research, which gathered from Hubei and Shanxi provinces and then growed in the experimental cropland at Huazhong Agricultural University. We did a series of studies on megasporogenesis,microsporogenesis, the development of female,male gametophyte and fertilization of Dioscorea zingiberensis by means of traditional paraffin wax sections. Elementary discussed its reproductive characteristics, the main results are as follows:1. Observations on the microspore genesis and the development of male gametes in Dioscorea zingiberensis revealed that the anther is 4-sporangiate and its anther wall is of basic type in the development, which comprises epidemis, fibrous endothecium, middle layer and glandular tapetum. The microspore mother cells undergo meiosis, and the cytokinesis is simultaneous. The tetrads are tetrahedral, occasionally decussate. Besides, mature pollen grains are 2-celled.2. Its pistil consists of three carpels, the inferior ovary has three locules and each locule has two ovules which are anatropous on axile placenta. The ovule is bitegminous and crassinucellate. The inner integument alone forms the micropyle. Archesporial cell divides to produce primary parietal cell and primary sporogenous cell. Sporogenous follow develops into megasporocyte, and undergoes meiotic division rusulting in linear of megaspores, the three micropylar megaspores degenerate, the chalazal megaspore is functional. There is only one layer of parietal cells at the stage of sporogenous cell, megaspore mother cell and tetrad. The functional megaspore undergoes three nuclear division resulting in an embryo sac of the monosporic Polygonum type. The mature embryo sac has seven cells and eight nuclei. Before fertilization, two polar-nuclei close up but do not fuse. Three antipodal cells degenerate lately.3. Fertilization is of premitotic syngamy type. The development of endosperm conforms to the Nuclear type and the embryogeny corresponds to the Onagrad type.