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作 者 ：黄衡宇;龙华;李鹂

期 刊 ：武汉植物学研究 2009年 27卷 3期 页码：233-241

关键词：小蓬草；菊科；胚胎学；

Keywords:Conyza canadensis(L.) Cronq, Compositae, Embryology,

摘 要 ：对小蓬草(Conyza canadensis)大小孢子发生、雌雄配子体形成、受精、胚及胚乳发育过程进行了研究,主要结果如下:花药四室,药壁由表皮、药室内壁、中层和绒毡层组成.表皮退化;药室内壁宿存,细胞柱状伸长,纤维状加厚;中层细胞退化较早,在小孢子母细胞减数分裂开始时仅存残迹;绒毡层于小孢子母细胞减数第一次分裂前期开始原位变形退化,属于腺质型绒毡层;小孢子母细胞减数分裂为同时型,四分体的排列方式主要为四面体形和左右对称形;成熟花粉粒多为3细-胞花粉粒,偶见2细-胞花粉粒.子房下位,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.珠心表皮下分化出大孢子孢原细胞,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4个大孢子直线形排列,仅合点端的大孢子发育成功能大孢子母细胞,胚囊发育为蓼型.两个极核在受精前融合为次生核,珠孔受精.胚乳发育属于核型,胚胎发育为紫菀型;具胚乳吸器.

Abstract:The microsporogenesis,megasporogenesis,the development of male gametophyte,female gametophyte,embryo and endosperm,and double fertilization of Conyza canadensis(L.) Cronq were studied in this paper.The results show as follows:the anther is tetrasporangiate and its mature wall comprises of an epidermis,endothelium,a middle layer and a single-layered tapetum;the epidermis degenerates;cells of endothelium persisted are columnar and with fibrous thick walls;the middle layer degenerates early and only a vestige can be observed at meiosis-I of microsporocyte;the tapetum belongs to glandular type,generally,is out of shape and degenerates early at meiosis-I of microporocyte;cytokinesis in the microsporocyte meiosis is of the simultaneous type,and the microspore tetrads are tetrahedral or isobilateral;pollen grains are mainly 3-celled,and occasionally 2-celled;the ovary is bicarpellate,unilocular,one ovules and basal placenta;the ovule is unitegmic,tenuinucellate,anatropous and with developed endothelium;archesporial cell of megaspore differentiates immediately below the nucellar epidermis and functions as megasporocyte after development,and then,the megasporocyte undergoes meitotic to form a linear tetrad,only one chalazal megaspore in linear tetrad becomes the functional megaspore;the embryo sac is of the Polygonum Type;two polar nuclei melt into a secondary nuclei before fertilization;fertilization is porogamous;the development type of the endosperm is Nuclear Type,and the embryogeny belongs to the Asterad Type;endosperm haustorium is present.

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