水稲における根部の発達およびアンモニア態窒素の吸収部位と体内分布との関係

抄録

This experiment was undertaken to study the influence of method of fertilizer application on root system, root-shoot relation and roles of root system in yield determining process. Paddy rice cv. Nipponbare was grown by water culture, and development of root system and distribution of nitrogen were investigated using a root-dividing method and ¹⁵N tracer technique. The results obtained are summarized as follows: 1. The total nitrogen content was remarkably reduced by the low concentration treatment before and after the panicle initiation stage. Inspite of the reduction of dry matter production, those roots elongating or emerging during this period showed marked development (Table 2). 2. At the heading stage dry weights of panicle, upper leaves and upper internodes in low concentration plot (L plot) were lager than those in high one (H plot). On the contrary dry weights of lower leaves and lower internodes in L plot were smaller than those in H plot although there was no difference of total dry weight between the two plots (Table 2). There also seemed the same trend about the nitrogen content in each part (Table 2). At the maturity stage weight of panicle in L plot was larger than that in H plot (Table 5). 3. Nitrogen uptaken during the ¹⁵N feeding treatment in L plot was larger than those in H plot, and it was distributed more into panicle, upper leaves and upper internodes, and lesser into lower leaves and lower internodes in L plot than in H plot (Table 3). In L plot labeled nitrogen existing in each part was transported from the root group (emerged during the 13th-16th leaf stage) at relatively high percentage. There was a lot of nitrogen left in a root group which was uptaken from the very root group (Table 4). 4. According to the distribution pattern of labeled nitrogen, difference of absorbing parts in root system did not have any effect on the distribution of nitrogen in a rice plant irrespective of the concentration treatment: H and L (Fig. 3).