论文部分内容阅读
报道非洲狼尾草（ＰｅｎｎｉｓｅｔｕｍｓｑｕａｍｕｌａｔｕｍＦｒｅｓｅｎ）的胚囊形成、胚胎发生与发育过程。非洲狼尾草的孢原细胞直接发育成大孢子母细胞，并由它分裂产生三分体。从大孢子母细胞发育至三分体的不同阶段，均会出现败育。性细胞退化期间，其周围的珠心组织中，常出现一至多个体积较大的无孢子生殖原始细胞。通常只有靠近珠孔端的１个无孢子生殖原始细胞体积进一步增大，并出现大液泡，发育成无孢子生殖单核胚囊。随后，其核经连续两次有丝分裂，形成无孢子生殖四核胚囊，胚囊内的４个核常聚积在珠孔端，４个核进一步分化形成１个卵细胞、１个助细胞和具两个极核的中央细胞，没有反足细胞。胚囊发育属于大黍型。其它的无孢子生殖原始细胞能发育到单核或二核胚囊阶段，而后核解体导致胚囊败育。胚的发生有两种类型：（１）早发生胚。大多数胚囊在开花前一、二天，次生核未分裂，卵细胞不经受精，自发分裂形成胚。（２）迟发生胚。少数胚囊的卵细胞不经过受精，但需要在开花后三、四天次生核分裂为多个胚乳核时才开始分裂。无论是早发生胚或迟发生胚，卵细胞在分裂前具有极性，珠孔端有大液泡，细胞质稀薄，合点端细胞质较浓。胚的发育经历球形胚、梨形胚和胚分化阶段。
Report on embryo sac formation, embryogenesis and development in PennisetumsquamulatumFresen. The African Pennisetum sporogenous cells develop directly into megaspore mother cells and divide to produce trisomy. From megaspore mother cell development to three different stages of tripartite, there will be abortion. During degeneration of sex cells, one or more bulky apoplastic reproductive primitive cells often appear in the surrounding nacre. Normally, only one conidia of primordial cells near the end of the micropyle grow further in volume and develop large vacuoles that develop into apomictic mononuclear embryo sacs. Subsequently, the nucleus was consecutively split twice to form apomictic tetranuclear embryo sacs. Four nuclei in the embryo sac accumulate at the ends of the peritoneal macrophages. Four nuclei further differentiated to form an egg cell, a helper cell and two A polar nucleus of the central cells, there is no anti-podocytes. Embryo sac belongs to the big millet type. Other apoplastic primordial cells can develop to the mononuclear or nucleus embryo sac stage, followed by nuclear disintegration that leads to abortion of the embryo sac. There are two types of embryogenesis: (1) Early embryogenesis. Most embryo sac in one or two days before flowering, the secondary nuclei are not divided, the oocytes are not fertilized and spontaneously divide to form embryos. (2) late embryo. A few embryos sacs do not fertilize, but need to split when the nucleus divides into multiple endosperm nuclei three or four days after flowering. Either early embryo or embryo late embryo, egg cells before the division has a polar bubble bead at the end of a large vacuole, thin cytoplasm, the junction of the cytoplasm more concentrated. Embryonic development experienced spherical embryos, pear-shaped embryos and embryonic differentiation stages.