1974 Volume 43 Issue 2 Pages 161-166
Raising the rice plant under the conditions of the different amount of basal nitrogen or nitrogen top-dressing and of the restricted nitrogen supply during the middle growth stage (70-90 in leaf number index), the authors tried to make a right evaluation of the nitrogen restriction treatment during the same stage. The grade of leaf color observed in the field, the percentage of stained length of leaf sheath by iodine solution as an index of starch accumulation and the nitrogen content in leaf blades in upper three leaves at the end of the treatment were checked. The following are the obtained results in this experiment. 1. A positive correlation was obtained between the leaf color grade and the nitrogen content in the upper three leaves as shown in the previous reports. On the other hand, the percentage of stained length of leaf sheath showed negative correlation with the nitrogen content in leaf blades and the leaf color grade. Consequently, the ratio of the leaf color grade to the percentage of stained length of leaf sheath showed a high positive correlation with the nitrogen content in leaf blades. 2. The grade of leaf color observed in the field, the percentage of stained length of leaf sheath and the ratio of them played an important role in the evaluation of the nitrogen restriction effect on the growth of rice. 3. According to these characteristics, tested materials were classified into 4 groups. For example, it seemed that the effect of nitrogen restriction was accomplished very well when the following conditions were satisfied at the same time; 1) when the leaf color was less than 2.5 in color plate index, 2) when the percentage of leaf sheath was about 50-60%, 3) when the ratio of 1) to 2) was less than about 0.05 and 4) moreover when the percentage of stained length of the third 1eaf sheath was nearly equal to that of the second one.
