Abstract
1) Length of top-internode of a culm was influenced by the amounts of top-dressing of nitrogen fertilizers at the stage of flag-leaf emergence. 2) Shortage of nutrients caused by cutting-off the roots or all leaf-blades at the above-mentioned periods accerelates shortening of the length of top-internode. Even in that case, top-dressing of nitrogen makes its shortening less. 3) Numbers of lower sterile spikelets were decreased, whenever the conditions which make the length of top-internode longer are given. The relation is shown in Fig. 1, with the case of var, Kogenmugi. 4) As a results of observations on the developmental process of each spikelets in ear, it is indicated that number of spikelets capable of ripening is determined during 15 to 5 days before the heading, and at the same time elongation of top-internode takes place. 5) A high correlation was obtained between the length of top-internode of a culm and the number of sterile spikelets which determines numbers of grain per ear.
