Studies on the nutrition of rice plant with reference to Helminthosporium leaf spot : Preliminary report : III The nutrient absorption as affected by the water temperature

[摘要] It is said that in the south-western parts of Japan the extremely high temperature during summer season exerts an unfavorable effect on the growth of rice plant, resulting in the serious occurrence of Helminthosporium leaf spot or "Akiochi", In order to ascertain whether such an occurrence of the disease or "Akiochi" in these districts is promoted by the abnormal plant nutrition due to high water temperature or not, some solution culture experiments were carried out in 1951, in which quantities of nutrients absorbed by rice plant during definite intervals were determined under different water temperature. Results of experiments are as follows: (1) The higher water temperature than optimum (about 30°C) reduced the absorption of nutrients in the order K2O>, SiO2>, NH3-N>, MnO>, P2O5 in one experiment (Table 1, A) and in the order SiO2>, K2O>, NH3-N>, P2O5>, MnO>, CaO in another experiment (Table 1, B) From this fact the serious occurrence of Helminthosporium leaf spot and "Akiochi" in the south-western parts of Japan may be partially attributed to the absorption inhibition of some nutrients such as silica and potassium caused by high water temperature. (2) The lower water temperature than optimum also reduced the absorption of nutrients in the order SiO2>, PiO5>, K2O>, NH3-N>, MnO>, CaO (Table 1, B). (3) Mitsui (1950, '51) has found that the uptake of nutrients is reduced by hydrogen sulphide in the order K2O>, SiO2>, NH3-N>, MnO>, MgO>, CaO and considered that when aerobic metabolism of root is retarded by hydrogen sulphide the absorption of ions of high value of hydration is far more extremely reduced than those of low value of hydration. The results of our work indicate that the reduction of nutrients absorption caused by the temperature relationships shows a striking similarity with the reduction caused by hydrogen sulphide as to the order of ions reduced. It may be suggested, therefore, that not only hydrogen sulphide but also supraoptimal or low temperature retards the normal aerobic metabolism of root and causes reduction of nutrient absorption according to the order of degree of hydration.

[学科分类] 农业科学（综合）