Studies on the Growth of Root Systems in Leguminous Crop Plants : IX. On the thickening growth of lateral roots

[摘要] 1. The experiment was carried out to make clear the characteristic of thickening growth of lateral roots in pea, soybean and alfalfa. These crops were selected respectively from three types showing different thickening growth pattern in main roots as stated in the previous paper. 2. Diameters, at 1 cm far from their branching points, of lateral roots which emerged along 20 cm from the base of main roots were measured by microscope at successive growing stages. 3. Trends in thickening pattern of lateral roots in each crop were as follows : A. pea Thickening of lateral roots was as little as that of the main root, and no thickening were recognized during winter time, while slightly thickened ones were found in April and May, however, even their thicker ones were not exceeding 1.5 mm in diameter (fig. 1-A, fig. 2-A). B. soybean The lateral roots emerging from base of the main root markedly thickened and their diameters reached to about 5mm, while the others that developed from the distal part between 7cm to tip of the main root did not nearly thickened (fig. 1-B, fig. 2-B and fig. 3). C. alfalfa Many thick lateral roots were found on the whole length of the main root, not only on basal but also on comparatively distal parts. Ten months after sowing, several thick lateral roots, more than 10mm in diameter, developed sporadically. More lateral thickeness is expected in both main and lateral roots at their final growing stages (fig. 1-C, fig. 2-C). 4. From these results, a close relation between the thickening growth types of the main roots and that of Iateral roots was recognized. Namely, in the little thickening type, the lateral, roots thickened also little; in the basal thickening type, the thick lateral roots concentrated at the basal part of the main root; and in the extensive thickening type, the thick lateral roots sporadically developed along the whole length of the main root.

[学科分类] 农业科学（综合）