The Formation Of Microspore And Megaspore, Development Of Male And Female Gametophytes And Fertilization In Fraxinus Mandshurica Rupr.

Fraxinus mandshurica Rupr. is dioecious plant. Pollen grains are 2-celled. The development of embryo sac is of Polygonum type. The fertilization is of premitosis type. Flowers are protandrous. There is a close relationship between the change (increase or decrease) of polysaccharide, lipid and protein with the suppliment of nutrition during the development of pollen. The embryology between Oleaceae and its relative families are compared and discussed. The similarity presents that these families are close in systematics.( 1 ) Micro-,megasporogenesis and the development of male and female gametophytes. The anthers is 4-microsporangiate. The development of anther wall is dicotyledonous type. The tapetum begins to glandular type. In the meiosis of microsporocyte, cytokinesis is simultaneous type. And microspore tetrads are tetrahedral or zygomorphic. Pollen grains are 2-celled. The ovary is 2-loculus with 2 anatropous ovules in each. The ovule is unitegmic and tenuinucellate. The megaspore mother cell undergoes meitotic division and forms a linear tetrad. The chalazal megaspore is the functional one. The development of embryo sac is of Polygonum type.(2) The corresponding relationship of the development of stamen and pistil. Flowers are protandrous. When pollen grains shed, female gametophyte is not mature yet, which is in the meiosis of megasporocyte.(3) Before fertilization, one synergid degenerates, and egg has clear polarity. The process of fertilization was observed and the results are as follows: After pollination, the pollen grains germinate and then the pollen tubes grow down the transmitting tissues in the style. The pollen tubes run through the micropyle to the embryo sac and release the contents with two sperms. The sperms are attached to the egg cell plasma membrane after pollination, and then enter into the egg nucleus. The chromatin show dispersion and the male nucleolus appear. The male and female nucleoli are combined and fused to form a single nucleolus, and the egg cell comes to be fertilized. The fertilization is of premitosis type. The polar nucleus fertilization is similar to the egg cell fertilization, but it proceeds quickly. The upper polar nucleus fuses with the sperm nucleus and then with another polar nucleus(the lower one). The resultant primaryendosperm nucleus contains only one nucleolus.(4) There is a close relationship between the change (increase or decrease) of polysaccharide, lipid and protein with the suppliment of nutrition during the development of pollen. The polysaccharide disapper from the wall layers gradually during the stage of meiosis. There is a great deal of lipid in the early stage of pollen mother cell, but there is neither amyloplastid nor protein grain showing. In the pollen mother cell the middle layers and tapetum accumulated a great deal of protein and lipid during the early stage of pollen mother cell, but there is neither amyloplastid nor protein showing. The middle layers and tapetum accumulated a great deal of protein and lipid during the stage of meiosis. Having finished meiosis the amyloplastid and lipid begin to appear in the tapetum and microspore tetrad, and the protein is induced. In the stage of microspore, there is a great deal of amyloplastid around the nuclear of microspore, and lipid is deposited on the wall of microspore and the radial, and on the endoscopic wall of tapetum cell. Meanwhile, the protein grain is not observed.(5) The results show that the embryological characteristics of Oleaceae is more similar to Scrophulariales than to Gentianales. We agree to the point of view that Oleaceae should belong to Oleales. The embryological characters of them are compared and discussed. The similarity presents that these families are close in systematics.