根瘤菌在大麦和水稻根上形成拟瘤的细胞结构

用3种方法使紫云英根瘤菌(Rhizobium astragali Huikui)、田菁根瘤菌(R.sesbania sp.)分别入侵大麦(hordeum vulgare L.)和水稻(Oryza sativa L.),形成拟瘤状组织。一是用一定磁场强度处理根瘤菌和植物,并接种培养。二是用含有水稻幼苗根提取物的培养基培养根瘤菌,接种水稻。三是重复别人用2,4-D外源激素处理植物,接种根瘤菌。镜检观察,用紫云英根瘤菌接种形成的大麦根拟瘤细胞结构非常精细,保持各种细胞器。有侵入线结构和根瘤菌从侵入线释放。根瘤菌被宿主细胞来源的膜包围,成为拟菌体。这些形态结构与豆科根瘤细胞相似,有共生状态特征,但拟菌体有泡状化现象。田菁根瘤菌入侵水稻根形成的拟瘤,在细胞间隙和细胞内都有细菌分布。受侵染的细胞结构粗糙,根瘤菌裸露,无胞膜包围。用2,4-D处理接种根瘤菌的拟瘤细胞结构也如此,但在维管系统内有大量密集的细菌存在。这种结构完全不同于豆科根瘤细胞结构,细菌与植物细胞的形态学相互关系是一种非共生联合作用。

CELL STRUCTURES OF PSUDONODULES FORMED ON THE ROOTS OF BARLEY AND RICE

There were three methods used to introduce the invasion of Rhizobium astragali Huakui and R. sesbania sp. into the roots of barley (Hordeum vulgare L.) and rice ( Oryza saliva L.) with subsequent formation of pseudonodules on their roots. One was to treat rhizobia and plants first with a certain strength of magnetic field, to inoculate rhizobia to plants, and then to culture them to-gather. Secondly, the rice plants were innoculated with rhizobium cultured medium containing the root extract of rice seedlings. And thirdly, plants were treated with exogenous 2,4-D before rhizobium innoculation. The cell structures of pseudonodules were very fine with organelles and infection threads, from which bacteria were released into the cytoplasm. Bacteria were enclosed in a paribac-teroid membrane becoming the bacteroid. These morphological structures were similar to those of legumes nodules with symbiotic characteristics, but the bacteroids were vesiculated. In the pseudonodules on rice roots formed by R. sesbania sp. cultured in the medium containing rice extract,the bacteria were distributed both in the intercellular and intracellular spaces. Here the structures of the infected cells were coarse containing free bacteria without paribacteroid membrane. The character of the pseudonodules formed after 2,4-D treatment were the same as those described above, but a large amount of bacteria were present in the central vascular system of parent roots. These kinds of struc- tures were completely different from those of legume nodules. The morphological relationship between the bacteria and plants could be attributed to an asymbiotic association.