Abstract: Plants of Leucaena leucocephala were inoculated with Rhizo-bia,and nodules were sampled for light and electron microscopic observation. The nodule of Leucaena leucocephala is composed of four Parts of different structural form, i. e. meristematic cell, cortical cell, vascular system and infected cell zone. Rhizobia infected cells by the infection thread that released into the host cytoplasm and gradually turned to N₂-fixation bacteroids. Bactero-ibs have three associated membrane systems:bacteroid cytoplasmic membrane, bacteroid cell wall, and plant-derived membrane envelope, or peribacteroid membrane. The early bacteroid was enclosed in a membrane envelope. It was observed that each membrane envelope in older infected cells contained more than one bacteroid. In the infected cells of mature nodule the bacteroids were enclosed in groups of two to five within their membrane envelopes. Prominent electron-translucent granules within the bacteroid were Probably Poly-β-hydroxybutyric acid. These changes are described in detail and the significance of the cell structural changes and their functional correlation to the development of root nodules are discussed in the present paper.

Key words: Leucaena root nodule, Rhizobium bacteroid, Cellular struc-ture and function of nitrogen fixing, Light and electron microscopic technique

摘要： 银合欢接种根瘤菌形成根瘤后,应用光镜和电镜技术观察。银合欢根瘤由分生组织细胞、皮层组织细胞、维管束系统和侵染细胞区域四个不同部分组成。根瘤菌借助于侵染线侵染细胞,释放进入宿主细胞质中,转变成固氮类菌体。最初每个包被膜内只含单独的类菌体,随后较老的侵染细胞中,每个包被膜内含有一个以上的类菌体。因此,成熟根瘤的侵染细胞可见有2~5个类菌体群集包被膜里,并且明显地累积PHB物质,显示电子染色透明颗粒。本文还讨论了上述变化的意义与银合欢根瘤细胞结构和功能的关系。

关键词: 银合欢根瘤, 根瘤菌类菌体, 细胞结构与固氮功能, 光镜和电镜技术