Excessive Tillering Research Articles

The Role of Root System of Rice Plant in Relation to the Physiological and Morphological Characteristics of Aerial Parts : V. The effects of nitrogen level and placing position of the fertilizer on the chalacteristics of root and aerial parts

Some relationships between the physiological and morphological characteristics of aerial parts in rice plants differing in plant type and other genetic characters, and root systems and root activities were presented in the previous papers (I to IV). In this study, a single variety, Nihonbare was used in order to find out effects of nitrogen level and placing position of the fertilizer on the chracteristics of root and aerial parts.The results obtained could be summarized as follows, (1) It was found that development and elongation of new roots were greatly retarded immediately after transplanting, when a higher level of nitrogen was applied as a basal-ferti-lizer. Therefore, a special caution should be paid to accelerate new root development through application of the optimum nitrogen amounts. (2) An excessive tillering of rice plants was observed at the stage of the maximum number of tillers, when a greater amount of nitrogen was applied as a basal-dressed fertilizer.This tendency was more pronounced as th amount of the upper roots was greater and the root activities were more active. However, the activities after this stage suddenly decreased, resulting in production of numerous invalid tillers. (3) On the other hand, the high root activity was maintained throughout the growth period, when the optimum amount of nitrogen as a basal-fertilizer was applied to deep-layer or to all the soil layers. As a results, a higher percentage of valid tillers was obtained in this case. (4) When the proper lelvel of nitrogen as a basal-feritilzer was applied to deep-layer and the whole layers, the activities of the total roots especially the lower nodal ones were active at the heading and ripening stages as compared with the activites in case of nitrogen, application to surface layer soil. The higher the lower-nodal root activity, the more chlorophyll was contained in the leaf and the slower destruction of chlorophyll in the leaf blade was taken place. It seemed very true that the higher yield was directly attributed to these relationships in case of nitrogen application to either deep-layer or the whole soil layers.

Studies on the Growth Habit and Tillering Process of Mat Rush

The procedure of the stem elongation and increasing tillers which are the important elements for determining the yield and quality of mat rush, had been investigated during the growing period from planting to harvesting in a paddy field. From the results of this studies, the growing characteristics of mat rush were cleared and the basic principles to improve the cultivation have been learned. Namely, so as to increase good mat rush, long stemmed and good quality ones have to be more harvested. The following three items should be taken: 1. From the results of this studies on the growth habits, it was ascertained that the new tillers which would grow to long good stem, had generated in the period from the last decade of May to the first decade of June. Therefore, its culture must be carried out to increase the number of new tillers growing in this period, and to accomplish the sufficient and vigorous development with them. 2. As a result of investigation on the relation of principal bud and new tillers, it was found that principal bud of new tillers which would grow to long stemmed, had already started the growth at the second decade of March. The fact suggests the new method for more yield of long rush by increasing the number of tillers on and from the second decade of March. 3. But excessive tillers grown prior to the first decade of April, namely the tendency of premature, result the development of many short stems and continuous growth of tillers. Therefore the growth advances for the earlier stage than normal, almost all the tips of long stems become rotted by over-ripening, and the yields of good long stems decrease which are to grow from late May to early June.