黄顶菊的大孢子发生、雌配子体与胚胎发育

Megasporogenesis,Development of Megagametophyte and Embryo in Flaveria bidentis (L.) Kuntze

用常规石蜡制片对黄顶菊(Flaveria bidentis (L.) Kuntze)大孢子发生、雌配子体和胚胎的发育过程进行了观察。黄顶菊雌蕊柱头二裂,2心皮,1室,单胚珠,基生胎座,单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层。珠心表皮下分化出孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成直列四分体,珠孔端的1个大孢子发育为功能大孢子,其余3个退化,胚囊发育为单孢型。单核胚囊经过3次连续有丝分裂,形成八核胚囊,成熟胚囊珠孔端有2个助细胞和1个卵细胞,胚囊中央有1个双核中央细胞,合点端3个反足细胞。胚胎发育过程分为球形胚、心形胚、鱼雷胚和成熟胚4个阶段。胚乳发育为细胞型,胚胎发育属紫菀型。在成熟种子中存在胚乳外套层。在种皮、苞片、胎座中观察到分泌结构和分泌物。

The megasporogenesis,megagametophyte and embryo development in Flaveria bidentis（L.） Kuntze were observed by using paraffin section method.The results showed that the stigma had 2 split,ovary was unilocular with bicarpellate,one ovule,basal placenta,unitegmic,tenuinucellate,anatropous ovule,and developed integumentary tapetum.Archesporial cell differentiated below the nucellar epidermis developed into megaspore mother cell,which formed a linear tetrad by meitotic divison,one megaspore at micropylar end developed into a functional megaspore,and the others degraded.The development of embryo sac was Monosporic Type.The mononucleate embryo sac underwent three successive mitosis to form mature embryo sac with seven cells,egg cell and two synergids near the micropyle,a central cell in the center of embryo sac,three antipodal cells in the chalazal.The embryo development could be divided into four stages,such as globular embryo,heart-shaped embryo,torpedo embryo and mature cotyledon embryo.The development of the endosperm was Cell Type,and that of embryo belonged to Asterad Type.The mature seed had an endosperm jacket layer,and the secretory structure and secretions were observed in seed capsule,placenta and bract.