Analysis of Yield-Determining Process and Its Application to Yield-prediction and Culture Improvement of Lowland Rice. : LXXXVII. Effect of nitrogen on dry matter production before the heading stage and the relation between the components in number of spikelets per unit area and dry matter production.

[摘要] 1. In case of an identical variety being used and sown on a definite date, the dry weight of rice plants at the neck-node initiation stage was positively correlated with the amount of nitrogen at that stage and, furthermore, with the number of panicles and with the number of differentiated rachis-branches. In case of used varieties and sown dates being different, however, the correlation coefficient was considerably decreased. 2. The dry weight increased during the period from the neck-node initiation stage to the late spikelet initiation stage was positively correlated with the amount of nitrogen absorbed during this period and also with the number of differentiated secondary rachis-branches. The photosynthate produced in the period was progressively increased in leaf-blades in proportion to the total quantity with increasing nitrogen content in leaf-blades at the neck-node initiation stage or at the late spikelet initiation stage and, moreover, with increasing amount of nitrogen in the whole plant absorbed in the period. 3. The more amount of nitrogen was absorbed by the plant during the period from the neck-node initiation stage to the late spikelet initiation stage, the more amount of dry matter was produced in the period, but the less amount of stored carbohydrates was found in sheaths and culms at the late spikelet initiation stage or at the heading stage. 4. The dry weight increased during the period from the late spikelet initiation stage to the heading stage was positively correlated with the amount of nitrogen absorbed in the period as well as the amount of nitrogen in the whole plant at the heading stage. 5. The amount of stored carbohydrates at the heading stage had no connection with the amount of nitrogen absorbed during the period from the late spikelet initiation stage to the heading stage. However, in case of an equal amount of nitrogen being absorbed by the plants by the time of late spikelet initiation, the amount of stored carbohydrates in sheaths and culms at the heading stage was progressively increased with increasing amount of nitrogen absorbed in the period. 6. A negative correlation was found between the dry matter increased during the period from the late spikelet initiation stage to the heading stage and the number of degenerated rachis-blanches.

[学科分类] 农业科学（综合）