Studies on Root System Formation in Leguminous Crop Plants : 3. Grouping of roots

[摘要] 1. The root system in legumes consists of different kinds of roots developed from various other organs in addition to the main root according to the kinds of crops and the way of cultivation. The author, therefore, considered it is necessary to classify and observe these roots of each group in order to make the study of root system formation easy and clear. Eleven species were used as materials in the present study. From this point of view, the author classified these roots according to their organs where the roots shot out as follows : (1) Main root system (2) Hypocotyl root system (3) Stem root system 2. Main root system is formed by roots shot out from the main root and it occupies usually great part of the whole root system in many sorts of leguminous crops. Hypocotyl root system is formed by roots originated from the both parts of hypocotyl and epicotyl. And these are frequently recognized even if it is under ordinary cultivation. Especially in case of mulching it is evidently promoted and frequently exceeds the main root system. Stem root system is the general name of the roots shot out from the parts except main root, hypocotyl and epicotyl. 3. The discrimination between the main root system and hypocotyl root system is practically difficult since there is no node in the plant body differenciating these two organs. On this subject, the author observed morphorogically this border comparing with following factors : (1) Occurrence of root hair (fig. 2) (2) Size of cells in epidermis and cortex (fig. 3) (3) Relation between the transition region of the primary vascular bundle and position of the first "branched-secondary root" (fig. 4, 6). 4. As a result in epigeal plants, the author recognized that the border position descriminated by the occurrence of root hairs coincided almost with other factors, (2) and (3) mentioned above. Judging from this fact, when we separate the border practically it is better to take up the initial secondary root as an indicator because it shows greater growth in branching, thickening and nodule formation comparing with hypocotyl roots. But in hypogeal plants, we can't observe that the border decided by the occurrence of root hairs does not coincide with other factors, (2) and (3). The author, therefore, decided to distinguish them by the cotyledonary node.

[学科分类] 农业科学（综合）