Morphological and Physiological Studies on Nodule Formation in Leguminous Crops : III The classification on the basis of the location and the origination in nodule formation

[摘要] In this experiment, 48 varieties of 17 species leguminous crops were used as materials. Each crops were planted in various experimental conditions, varying in amount of nitrogen spplied, light intensity and method of inoculation, ie, the artifitial inoculation in soil cultur, or the natural inoculation in field cultur and the guartz sand cultur in different inoculate of nodule bacteria, in the suitable season for each crop. The external and internal observations were made on: 1) the location of nodule formation on root system, the nodule numbers and weights. 2) the site of nodule origin and the developmental prcocess of nodule formation with the histological methods. during from the germinating stage of host plants to the flowering stage at various intervals of time. The data obtained with the different varieties of same species are not tabulated separately in this paper. The results obtained are as follows: (1) The classification on the basis of the location of nodule formation on root systems. I-A : The primary and lateral roots type: the nodule formation was found on the primary and all the lateral rootlets and the nodule's size and number were most large in the basal portion as compared with the apical portion in same root. I-B : The lateral roots type: the nodule formation occurred only on the lateral roots, even though the host plants were growing under widely different conditions, and the graduation of nodule formation in the same root are identical with I-A type. (2) The classification on the basis of the site of the first infection cell in host tissues. II-A : the outer -layers in primary cortex type: the infection is limited to the outer layers in primary cortex ; endodermis, pricycles and central steles of the root are not directly concerned in their formation other than in the production of the vascular system necessary in the later stage of nodule development. the site of penetration of nodule bacteria into host tissues and of formation of the first infection cell have not correlated with the structur of central stele in roots, therefore, the location of nodules on root were at randam in the external view. II-B the inner-layers in primary cortex type : the nodules have originated by division of the parenchymatous cells in the inner layer of primary cortex in the host plant, usually opposite protoxylem points. for that reason, the location of nodule formation on root were limited in under lyning opposite the prot. xylem point. II-C The axil of lateral root type: the origin of nodules is in pericycle cells adjacent and in juxtaposition to the protoxylem strand from which a rootlet had emerged. therefore, All nodules were located in rootlet axil. In the peanut, this arrengement was conspicuous since the root system of this species consists of a central taproot, along which lateral roots arise in an orderly alignment of four vertical rows, owing to the tetrarck pattern of the xylem. This classification have not correlated with the arc pattern of host roots, the apigeal or hypogeal on germinating stage of host crops and the numbers of cell layers in primary cortex of host, but the good agreement was obtained between the results of this experiment and the cross-inoculation groups on nodule bacteria.

[学科分类] 农业科学（综合）