A Preliminary Report on the Form of the Root System in Rice Plants

[摘要] As the knowledge of the root system in crops is important for their rational cultures, it has been studied by occidental investigators, using the materials of crops cultivated therein. Information on the form of the rot system in the chief tropical crops has been made public, while it has not been the case with our rice plants. The method of observation of the root system in rice plants taken by the author was so-cal'ed direct method, instead of washing soil away from roots by water jets. (We may call it the washing method.) Fibrous roots of rice plants are so delicate that the pressure of water necessary to remove soil brakes and carries them away. A trench is excavated, one side being vertical and about one c m apart from the rice plant. With a sharp "Kiri, " a, needle-like gimlet, all roots developing in the vertical layer of soil, two c m thick, are exposed thoroughly by carefully removing the soil little by little; to the minutest bit of root. Examining the exposed root system developing in the layer, measurements of its extreme depth, its lateral extent and its working depth are made. To draw the figure exactly, it is most satisfactory to trace all roots with a pen of Indian ink on the surface of a, glass plate, supported in contact with the vertical layer of soil. Thus, root-maps are drawn. To have an aggregate root-map, all root-maps belonging to a kind are traced together on one sheet of tracing paper. By investigating the collected root system on the aggregate root-map, discussions are made. (The map having no number in an five figures in the full paper is the corresponding aggregate root-map respectively.) The general outline of the extent of root development in each aggregate loot-map is drawn approximately. It is sometimes an ellipse or an inverse oval. The solid body of soil, enclosed in the surface whose section is the outline of the loot system; the author calls the occupied soil body of the root system. The variety of rice plants used in the investigation is late Shinriki cultivated by two different, methods. The one is Sugimatsu's method, a, special dry culture which consists of planting in an irrigated rice field and then ceasing the irrigation until the middle of August, a little before the heading time. the other is the standard method. The response of roots of rice plants to irrigation water is very remarkable. The roots in the dry culture penetrate straight downward, forming a narrow long root system, to absorb water from a deeper part of soil; because water supply is rather-scarce near the surface of a field. The body occupied by the root system is elliptically long, before the heading time. All fibrous roots are coarse, bent, rich in branching roots and root hairs, as if they were those of dry crops. (ref. Fig l) For roots of the newly transplanted rice plants in the standard culture, it is not necessary to grow downward for the water in deep soil, because they call take up as much water as they want freely near the surface of an irrigated field. Consequently, rice plants have a flat shallow root system, the occupied body being elliptically flat, in this case. The fibrous roots are quite different from those of the dry culture. (ref. Fig 2) Rice plants of the standard culture wilt and die in a short time after. Irrigation water has been withdrawn, notwithstanding they thrive well without irrigation water, in the dry culture. Having the deep long root system, rice plants of the dry culture can absorb water from deep parts of soil. Thus, they generally stand a drought better. After heading, the rice plant of the dry culture has a matured root system whose form consists of two types; flat and long. (ref. Fig 4). The second occupied body flat elliptical is newly formed on the primary occupied body of a long elli tical shape. At an early stage, the dry cultured rice plants showed the single form of the flat root system. (ref. Fig 1). [the rest omitted]

[学科分类] 农业科学（综合）