摘要
光镜的观察确定了鹤顶兰（Ｐｈａｉｕｓ ｔａｎｋｅｒｖｉｌｌｉａｅ （Ａｉｔｏｎ） Ｂｌ．）胚囊发育属单孢子蓼型。应用免疫荧光标记技术及共焦镜观察了胚囊发育过程中微管分布的变化。当孢原细胞初形成时，细胞内的微管呈网状分布。之后，孢原细胞体积增大发育为大孢子母细胞。大孢子母细胞延长，进入减数分裂Ⅰ。微管由分裂前的网状分布变为辐射状排列。二分体的两个细胞内的微管分布一样，呈辐射状。四分体的近珠孔端的３ 个大孢子解体，细胞内的微管消失。靠合点端的功能大孢子内有许多微管呈网状分布。当功能大孢子进入第一次有丝分裂时，细胞内的微管由网状变为辐射状，从核膜伸展至周质。再经两次有丝分裂形成八核胚囊。在核分裂之前微管一般是呈网状分布并紧包围着核。在分裂期间二核和四核胚囊都呈极性现象，微管系统也呈极性分布。微管在八核胚囊内的分布变化情形特别复杂。首先，八核分别作不同程度的移动，其中两个核移向胚囊中央，珠孔端和合点端的３ 个核分别互相靠拢，形成３ 个区，即中央区、反足区和卵器区。胚囊未形成区时，８ 个核都被网状分布的微管包围着。当胚囊明显分成区时，反足区内的微管仍作网状分布。中央区的微管分布则趋疏松，形成篮形结构，包围着液泡和两个极核。
In nun orchid (Phaius tankervilliae (Aiton) Bl.) embryo sac development follows the monosporic pattern. Changes in the pattern of organization of the microtubular cytoskeleton during megasporogenesis and megagametogenesis in this orchid were studied using the immunofluorescence technique and confocal microscopy. At the initial stage of development the microtubules in the archesporium were randomly oriented into a network. Later, the archesporial cell elongated to form the megasporocyte. The cytoskeleton in the elongated megasporocyte was radially organized in which microtubules extending from the nuclear envelope to the peripheral region of the cell. The megasporocyte then underwent meiosis l to form a dyad. The dyad cell at the chalazal end was larger than the cell at the micropylar end. Microtubules in the dyad cell were radially oriented. The dyad underwent meiosis to give rise to a linear array of four megaspores (i. e. tetrad formation). The chalazal far most megaspore survived and became the functional megaspore, which contained a set of randomly oriented microtubules. The microtubules in the other 3 megaspore disappeared as the cells degenerated. The functional megaspore then underwent mitotic division giveing rise to a 2 nucleate embryo sac. The nuclei of the 2 nucleate embryo sac were separated by a set of longitudinally oriented microtubules which ran parallel to the long axis of the embryo sac. Each nucleus in the embryo sac was surrounded by a set of perinuclear microtubules. The 2 nucleate embryo sac again underwent mitotic division to form a 4 nucleate embryo sac. The division of the two nuclei was synchronous. But the orientation of the division plan of the two spindles was different (i. e. the spindle microtubules at the chalazal end ran parallel with the long axis of the embryo sac and those at the micropylar end ran at right angle to the axis of the embryo sac). The 4 nuclei of the 4 nucleate embryo sac were all tightly surrounded by randomly oriented microtubules. Later the paired n
基金
香港球槎基金
关键词
兰科
鹤顶兰
微管
胚囊
发育
共焦显生镜
Mun orchid
Microtubules
Department of embryo sac
Confocal microscopy
