多花地宝兰胚囊和胚发育的细胞学研究

为探讨多花地宝兰(Geodorum recurvum)胚胎发育的系统分类学意义,采用石蜡制片法对多花地宝兰胚囊和胚的发育进行解剖学观察。结果表明,在开花前,多花地宝兰胚珠原基发育缓慢,开花授粉后胚珠原基快速发育成"树状二杈分枝结构",随后在"分枝结构"末端形成孢原细胞,开始胚囊发育。多花地宝兰的胚囊发育属于单孢蓼型胚囊,胚珠具有双层珠被。孢原细胞形成后,经过细胞膨大延长发育形成胚囊母细胞,胚囊母细胞经过减数分裂形成线性四分体,在珠孔端形成1个功能大孢子,功能大孢子经过3次有丝分裂形成8核胚囊。多花地宝兰的胚发育具有藜型和紫苑型两种方式。双受精完成后,多花地宝兰合子进行一次橫裂后形成基细胞和顶细胞;基细胞经过多次分裂形成细胞团,细胞团中的细胞向不同方向膨大延长形成多个胚柄细胞;顶细胞有两种分裂方式,一种是横裂形成藜型胚,一种是纵裂形成紫苑型胚。因此,推测多花地宝兰在兰科植物系统分类学上属于较为原始种。

Cytology Studies on Embryo Sac and Embryo Development of Geodorum recurvum

In order to understand the systematical significance of Geodorum recurvum in Orchidaceae, the development of both embryo sac and embryo were observed by using paraffin section method. The results showed that ovule primordium of G. recurvum developed slowly before blooming, and then developed quickly into "tree-like two-branch branching structure" after pollination, archesportial cells differentiated at the top of branches, and the embryo sac began to develop. The development of embryo sac belonged to polygonum type, ovule had two layers of integument cell. Archesportial cell developed into embryo sac mother cell by expansion and enlongation. The embryo sac mother cell formed linear tetrad by meiosis, and one functional megaspore at micropylar. Functional megaspore divided into 8-nucleu embryo sac by three times division successively. The developement of embryo had chenopodium type and asterad type. After double fertilization, the zygote divided into a basal cell and an apical cell by a transverse division. The basal cell formed cell group by division many times, and the cells formed suspensor cells situated through expansion and enlongation along different directions. The apical cell had two division type, one formed quinoa type embryo by transverse division, another did asters type embryo by longitudinal division. Therefore, it was suggested that the evolution of G. recurvum belonged to primitive in Orchidaceae.