Microstructural And Ultrastructural Studies On Root Nodules Of Important Leguminous Plants Grown On Shaanxi And Gansu Flora Loess-Plateaus

Leguminous plants were the important resources of nitrogens in ecosystem, the nitrogens they fixed were 40 persent of the biological nitrogen fixation on the earth. So the structure of nitrogen fixation,which is the root nodule, was worth of being studied systematically.There were about 200 species subordinated to 49 genera in Leguminous growed on the Flore Loess-Plataus, which were significant of improving soil and protecting ecosystem. This paper using 34 species in 21 genera on the shaanxi, gansu Flore Loess-Platau, comparatively studied the morphological and structural characteristics of root nodules from different species, then studied the ultrastructure of root nodules and their bacteriods of Trifolium repens Linn., Medicago sativa Linn, and Astragalus adsurgens Pall.cv. huangheensis. The results were as follows:Comparative anatomy on root nodules of 34 species leguminous plants grown on the Flora Loess-Plateaus were studied by methods of paraffin-sectioning. The 34 root nodules grew from main roots and lateral roots or only lateral roots. Round, long round or scalloped root nodules are white, or pink. Some root nodules branched. All the nodules are composed of four parts, ecto-entad they are: the protect layers, cortex, sheath cell layers and center tissue(tissue infected). The results of statistics showed the cell layer numbers of the four parts were different in different root nodules. There were no positive correlation between the percentage of tissue infected and percentage of center tissue.The structure of root nodules in Trifolium repens Linn, andMedicago sativa Linn, were studied by methods of parafFm-sectioning and ultra-thin-sectioning. the nodules were composed of four parts, ecto-entad they were: the protect layers, cortex, sheath cell layers and center tissue(tissue infected). In the infected cells of center tissue , there were a lots of mitochondron, Golgi bodies and endoplasmic reticulum. The bacteroids in Trifolium repens were round or oblong, which had distinct peribacteriod membranes, cell wall and plasma membrane, the peibacteriod membranes were active during the development of bacteriods. The peribacteriod membranes of neighorbing bacteriods where there were many endoplasmic membrane, Golgi bodies and vesicles fused together. While the bacteriods in Medicago sativa were oblong, linear-clavate, or branched. There were lots of ribosomes and fibrilsome nuclei materials in bacteriods of both species.The structure of root nodules in Astragalus adsurgens Pall.cv. huangheensis were studied by methods of paraffin-sectioning and ultra-thin-sectioning. the nodules were composed of four parts, ecto-entad they were: the protect layers, cortex, sheath cell layers and center tissue(tissue infected). In the infected cells of center tissue , the senescence of bacteroids has centain laws.