Abstract: Nodules of three legume species, Sopora alopecuroides, Astragaous sp. and Vicia costata in Xinjiang are studied on their morphological characteristics with light microscopy and EM. It is found that the shape and structure of nodules are influenced by local environment. Under long-term aridity and high soil temperature, they have a thicker cortex, which as a flexible barrier supports a moderate microenvironment for bacteroids within the nodule. No relationship between ultrastructure of nodule's central zone and dry environment has been found in this study, although there is an obvious structural difference among tested legume species.

Key words: Leguminous plant, Nodule cortex, Xinjiang arid area