Chloris roxburghiana Schult.（禾本科）之胚胎形成過程

Embryology of Chloris roxburghiana Schult. (Poaceae)

Chloris roxburghiana花藥為四孢子囊型。花藥壁的發育屬單子葉植物型，在表皮細胞下面有三層花藥壁。花藥的營養層為腺質型，其細胞共二核。小孢子母細胞成二行排列，經由一般的減數分裂後形成兩邊相同的小孢子四分粒。細胞質分裂屬連續型。花粉粒被釋出時具單孔及三核。具三至四個精子的不正常花粉粒亦被觀察到。子房內含一橫生胚珠，胚珠具一雙珠被及薄珠心。大孢子母細胞經減數分裂後形成T字型的大孢子四分粒。遠離珠孔的大孢子發育為胚囊，胚囊的發育屬單孢子蓼型。授精後，胚囊在朝遠離珠孔的一端呈盲腸狀。反足細胞被此側盲腸取代。胚乳的發育為核型，而胚的發育為紫苑型。

Anthers are tetrasporangiate. Anther wall develops in a Monocotyledonous manner, leading to the formation of three layers below the epidermis. Anther tapetum is of Glandular type and its cells become two-nucleate. Microspore mother cells are arranged in two rows and normal meiosis leads to the formation of isobilateral microspore tetrads. Cytokinesis is of the successive type. Pollen grain is 1-porate and 3-celled at the time of shedding. Some abnormal pollen grains with three to four sperms have been observed. The ovary contains a single bitegmic, hemianatropous and tenuinucellate ovule. Meiosis in megaspore mother cell leads to the formation of T-shaped tetrad of megaspores. The chalazal megaspore is functional and embryo sac development follows monosporic Polygonum type. Embryo sac after fertilization shows prominent caecum towards the chalazal end. Antipodal cells get displaced to this lateral caecum. Endosperm development is of the nuclear type and embryogeny follows Asterad type.