Morphological and Physiological Studies on Nodule Formation in Leguminous Crops. : VIII. On the nitrogen fixing systems in nodules of pea plants.

[摘要] Two phases of the nodule bacteria and nodule development complex have been studied; (a) the growth and the advancement in life cycle of nodule bacterium during nodule formation, and (b)the histology of nodules. (1) The developmental process in nodule formation in leguminous plants could be divided into five stages as follows: a) The infection stage, b) the embryonic stage, c) the stage of differentiation, d) the stage of elongation, and e) the stage of maturation and the senescent stage by a conventional means. The increase in total number of bacteria in nodule was closely correlated with the increase in nodule diameter, in volume of bateroid tissue and in nodule dry weight, But it did not show any direct relation with the progress of nodule forming stages, A rapid decrease was detected with bacteria number during the senescent stage. The nodule bacteria were classified into "rod-shape bacterium" and "bacteroid-shape bacterium" according to their life cycle stage by morphological and physiological points of view. The rod-shape bacteria were observed from the infection stage to the embryonic stage and the rod-shape bacterium and the bacteroid- shape bacterium were detected in a bacteroid tissues from the stage of differentiation to the stage of maturation. At the senescent stage, however the bacteroid-shape bacterium disappeared in bacteroid tissues, and as a result, only the rod-shape bacteria were observed. (2) Leghemoglobin formation in bacteroid tissues of nodules was detected in the stage of differentiation. At first it appeared at the base of the bacteroid tissue, and then increased until the entire tissue showed the red pigment at the stage of maturation. At the senescent stage, the red pigment color changes to green pigment starting from the base of bacteroid tissue viz. ……leghemoglobin(red)→legcholeglobin (green)……. The distribution area of green pigment also enlarged in the same manner as in the red pigment. In the final stage (senescent nodule) the nodule pigment change occurred again in the same manner as before. viz.……legcholeglobin (green)→legmethemoglobin (brown). (3) The change in distribution of leghemoglobin and starch in bacteroid tissues of nodules was found to be closely synchronized with the bacteroid-shape bacteria. (4) The N2 fixing power of nodule is dependent on the physiological conditions of the host plants such as the total nitrogen contents.

[学科分类] 农业科学（综合）