沙棘根瘤及根瘤内弗兰克氏菌形态的显微观察

Microscopic Observation of the Root Nodule and the Morphology of Frankia in Root Nodules of Hippophae rhamnoides

沙棘根系可以与土壤中的弗兰克氏菌形成特殊的共生固氮器官——根瘤。以中国沙棘为材料,利用光学显微镜和透射电子显微镜对根瘤形态、瘤瓣解剖结构和根瘤中弗兰克氏菌的存在形式进行了较为细致的观察。结果表明,沙棘根瘤是以单个瘤瓣为基本单位、经多次二叉分枝形成的珊瑚状结构;瘤瓣的各个组织均有侵染细胞的存在,其中外皮层和中皮层外侧区域的侵染细胞分布密集,中皮层的内侧区域以及中柱内侵染细胞相对较少;弗兰克氏菌在侵染细胞内以菌丝体、泡囊和孢子囊3种不同的形式存在。这些观察结果为相关研究提供了更为清晰和直观的基础资料。

The roots of seabuckthorn(Hippophae rhamnoides) can form a special symbiotic nitrogen-fixing organ,i.e.,the nodule,in association with the bacteria Frankia in soil.In this paper,the morphology and the anatomical structure of the nodules as well as to the existing forms of the bacteria in nodule cells of seabuckthorn were observed by using optical and transmission electron microscopes.The results showed that the adult nodules presented a coralloid structure which was formed by multiple-dichotomously branching of a single nodule as the basic unit.In the nodule,the infected cells existed in all of the tissues,especially in the exodermis and the outer layer of the middle of the cortex with dense distribution,while in the medial region of the endermis and the stele,relatively few infected cells were observed.In the infected cells,Frankia was present in three different forms:mycelium,vesicles and sporangia.These observations would provide a clearer and more intuitive basis for the relevant research.