Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice : LXXXIII. Relation between the plant types after heading and the varieties differing in the maturation period.

[摘要] In the previous paper (No. 73) the authors pointed out that the plant type after heading has a close relation to the percentage of ripened grains under luxurious growth conditions and, therefore, the study of plant types is quite necessary for maximizing the yield of rice. In the other papers (No. 58 and 66) they also clarified that the top-dressing of nitrogen at a definite growth stage makes the plant elongate a definite leaf-blade, leaf-sheath and internode, while the restriction of nitrogen supply shortens each of them. On the basis of these facts, the authors considered that under the rice cultivation in which only basical fertilizers are applied and not top-dressed at all, if the varieties differing in the maturation period are transplanted on an identical date, the effectiveness of nitrogenous fertilizers will also appear on an identical date, as a result of it, the longest leaf-blade will be found on upper nodes in short-term varieties, while it will be found on lower nodes in long-term varieties. For examining this point, the authors investigated nine varieties differing in the maturation period for three seasons, confirming the following facts. The longest leaf-blade is found on the second node from above in very short-term varieties, on the third node in short-term and medium-term varieties, and on the fourth node or fifth node in long-term varieties. In other words, the longest leaf-blade appears on the lower node as the variety becomes longer in the maturation period. As to the length of leaf-sheaths, the upper most one is always longest in most cases. But the second longest oneis found on upper nodes in short-term varieties and on lower nodes in long-term varieties as in case of leaf-blades. Since the growth of a leaf-sheath is synchronized with that of the immediate upper leaf-blade, the second longestleaf-sheath is found on the third node from above in very shortterm varieties, on the fourth node in short-and medium-term varieties, and on the fifth or sixth node in long-term varieties.

[学科分类] 农业科学（综合）