On the yielding efficiency of Japanese rice varieties. : Stem length.

[摘要] 1. As one of the series of the writer's reports concerning the yielding efficiency of Japanese rice varieties, the data on the length of stem of paddy rice plants in Japan are reported. 2. In all the agronomic varieties of the paddy rice of Japan studied, the minimum of stem length is 44 cm, and thg maximum 140 cm, the mode being 92 cm, the mean 91.21 cm, and the σ 10.49 cm. The distribution is a very typical monomodal symmetric curve. 3. The distribution curve of the stem length of rice varieties in each prefecture presents a typical monomodal symmetric one. The minimum of the mean is 80 cm in Akita, 81 cm in Aomori, 82 cm in Fukusima, etc. The maximum is 100 cm in Gumma, 98 om in Nara, 96 cm in Yamagata, etc. 4. A close negative correlations were found between the stem length and number of stems per tubo, the days from seeding to heading, and the latitude coefficient etc., while a close positive correlations were made clear betwen the stem length and the yield per tan, prefectural average yield per tan, and the mean temperature, etc. 5. From 1931 to 1940, a diminution of the stem length occurred according to the straightline drawn by means of R=-0.6114y+97.49 cm. 6. The positive yearly correlations were found in each prefectures between the stem length and yield per tan, - the mean temperature from April to November, - the mean temperature of July. Negative correlation were made clear betwen the stem length and the heading date, the number of stems, the amount of rain fall from April to November, and the sun shine from April to November. 7. The number of stems shows a closer correlation with the yield, than that between the length of stems with the same, if considered by the usual correlation coefficient. But the stem length shows a closer correlation with the yield, when considered from the least square equation of the yearly tendency. 8. Sembon-asahi and Norin no.1, showing the mean stem lengths 73 cm and 79 cm respectively, are the representative short stem varieties, while Watarifune and Kokuryomiyako, the mean stem length of which are 102 cm and 104 cm respectively, are the standard long stem varieties. 9. By the "deviation from the mean method" which I proposed in order to present the relative value of a given variety compared to the mean value of the population of the varieties concerned, the "deviation from the mean value" of each variety is calculated. The values are as follows. Sembon-asahi - 17.0 cm, Norin no.1 -13.3 cm etc. (shorter varieties) Watarifune +7.0 cm, Kokuryomiyako +12.3 cm etc. (longer varieties). The tendency "deviation from the mean method" coincide with the tendency of absolute numbers. 10. We can calculate the theoretical length of the stem of any variety at any locality by adding or substituting the "deviation from the mean value" from the local stem length. 11. Among the varieties of rice plants, the correlations betwen the stem length and the yield per tan, the number of head per plant, and the number of head per tubo are negative and significant, while the correlation between the absolute stem length and the "deviation from the mean value" of the stem length is positive and distinct.

[学科分类] 农业科学（综合）