Sporogenesis And Gametogenesis Of Camellia Parvilimba And Camellia Parvilimba Var. Brevipes

Sect. Theoppsis belongs to Camellia, Theaceae. The ambiguity of Camellia mainly exist in Zhang Hong-da system and Min Tian-Lu system in China. There are 46 species in the Sect. Theoppsis of Zhang Hong-da system, but Min Tian-Lu consider that there are 19 species in the Sect. Theoppsis. In Zhang Hong-da system, Camellia parvilimba var. brevipes is as the variations of Camellia parvilimba. But in Min Tian-Lu system, Camellia parvilimba and Camellia parvilimba var. brevipes are one species.In this study, the flower buds of C. parvilimba and C. parvilimba var. brevipes in different embryo developmental stages are used as the basic materials, which are gathered from international camellia species garden in Jin Hua, Zhe Jiang. Through paraffin section, image capture, analysis and so on, sporogenesis and gametogenesis of Camellia parvilimba and Camellia parvilimba var. brevipes are done a series of studies. According to the microstructure of the two plants' embryo development and the developmental stages of buds, the main results are as follows:1. C. parvilimba and C. parvilimba var. brevipes have multiple stamens. Observation on the microspore genesis and the development of male gametes in C. parvilimba and C. parvilimba var. brevipes reveal that the anther is 4-sporangiate and its anther wall is of basic type in the development, which comprises of one epidemis, one fibrous endothecium, two middle layer and one glandular tapetum. The microspore mother cells undergo meiosis, and the cytokinesis is simultaneous. The tetrads are tetrahedral. Besides, mature pollen grains are 2-celled. There are 3 apertures. Epidermis persistent forms protection function. Endothecium fibrous are thickening in mature pollen. When the mature pollen begin to disperse, endothecium fractures where is not thicker. The disintegration of the middle layer start in the stage of microspore mother cell, which provide nutrition for the development of tapetum and microsporocytes. Tapetum appears multicore phenomenon when microspore mother cells begin mitosis, and begins to disintegrate in the tetrad stage. Tapetal cells play the role of providing nutrition substances for the development of microsporocytes.2. The ovary is 3-loculus with 2-3 anatropous ovules in each, which are axile placentation. The ovule is bitegminous and tenuinucellate. Micropyle is formed by internal integument. Pistil stigma is lobed, and stylar canal is hollow. Archesporial cell which is under nucellar epidermal cells directly develop to megaspore mother cell. Megaspore mother cell meiosis forms a dyad. The micropylar dyad cell degenerates, and the chalazal dyad cell is functional megaspore. The functional megaspore undergoes three nuclear division resulting in an embryo sac of the Allium-type. The mature embryo sac has seven cells and eight nuclei. Before fertilization, two polar-nuclei close up and do fuse or not. Three antipodal cells degenerate earlier.3. After pollination, the pollen grains germinate and then pollen tubes grow down the transmitting tissues in the style. Before fertilization, two synergids degenerat, and the egg has obvious polarity. The sperms are attached to the egg plasma menbrane after pollination, and then enter into the egg nucleus.4. According to the embryonic development's microstructure of the above two kinds of plants, and combining with the external development situation of the flowers, the buds growth of the C. parvilimba and C. parvilimba var. brevipes can be divided into several different developmental stages, germinating buds, young buds, budlets, big buds, full buds, be opening buds, ovary tips outstanding buds, flowers completely open. Through the compared of the internal embryonic development stage and the external shape of the pistil and stamen, the internal embryonic development period can be inferred with the external shape intuitively.5. The research shows that the embryonic development's characteristics of the C. parvilimba and C. parvilimba var. brevipes are basically the same. And the embryology feature of the two plants are basic similar with Camellia which have been reported. Compare with the relatively primitive external shape, the embryology characters are relatively evolutionary. The embryology characters and the external shape characteristics of the two plants express asynchronous phenomenon.Microsporogenesis, Megasporogenesis and the development of male and female gametophytes of C. parvilimba and C. parvilimba var. brevipes are first systematically studied. The research will helpful for accumulating basic data of Theaceae embryology research. Morphological and scalar feature of pistil and anther of C. panilimba and C. parvilimba var. brevipes are described qualltatively and quantificationally. It contributes to inferring the stage of internal embryonic development by the exterior morphology. Comparing the embryological feature of C. parvilimba and C. parvilimba var. brevipes with other Theaceae relatives, which can make further illustrate of the phylogenesis of Theaceae. On a long view, the research will also provide reference data for the study of the C. parvilimba's and C. parvilimba var. brevipes's genetic improvement, establishment of seed orchard, improving setting percentage and so on.