In sweet sorghum, the pattern of internode characteristics, which is drawn by plotting the length, diameter and the volume of internodes against internode position, is an important characteristic of the stem structure. The pattern is also considered to be an important trait for analyzing the process in which the stem yield and stem volume are determined. We examined the relationship between the stem volume and the pattern of internode characteristics in sweet sorghum cultivars with different earliness in maturity in the Tohoku region, and also analyzed the stem volume in association with their growth process over three years. As for the internode diameter pattern, all cultivars had almost the same pattern every year, while, in regard to the internode length pattern, the number and position of peaks varied depending on the year and the cultivar. In 2011, with a high temperature early in the growth, all cultivars had the largest stem volume and the lower internodes tended to be shorter and thicker than in other years. In addition, stem elongation began at almost the same time over three years. These results showed that a high temperature during the early growth stage accelerated the rate of leaf expansion, resulting in an increase in the number of basal non-elongated internodes and thicker stem caused by relative depression of elongation of basal internodes.
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