Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice. : LXXXV. An investigation on the percentage of ripened grains from the point of analytical view of the number of spikelets per unit area.

Abstract

After classifying the rice plants which grown under several cultural conditions in last few years into the several groups according to the number of spikelets per unit area, the authors studied the percentage of ripened grains from an analytical investigation of the number of spikelets per unit area, obtaining the following results. 1. When the number of spikelets per unit area was extremely small, no definite relation was found between the percentage of ripened grains and any component of the number of spikelets per unit area (i.e. the number of panicles per unit area, that of spikelets per panicle and that of primary and secondary rachis-branches per panicle). 2. The percentage of ripened grains showed a tendency to decrease progressively with an increase in the number of spikelets per unit area, spikelets per panicle and secondary rachis-branches per panicle, while it seemed to increase with an increase in the number of panicles per unit area. 3. When the number of spikelets per unit area was extremely large, the percentage of ripened grains was positively correlated with the number of panicles per unit area and negatively correlated with the number of spikelets per panicle as well as the number of secondary rachis-branches. 4. In case of the number of spikelets per unit area being large, the fact that the percentage of ripened grains decreased with an increase of the number of spikelets per panicle could be explained from the fact that the number of spikelets per panicle increased with a decrease of the amount of carbohydrates stored in sheaths and culms before heading and that of photosynthetic products after heading.