Analysis of Yield-Determining Process and Its Application to Yield Prediction and Culture Improvement of Lowland Rice : LXXXI. Combined effects of air-temperature, water-temperature, shading and the amount of fertilizers in seedling period on the characteristics of seedlings of rice plants.

[摘要] Growing rice seedlings under the various conditions of all possible combinations of air-temperatures (16°C·21°C·31°C and 36°C) and water-temperatures (16°C·21°C·31°C and 36°C) and furthermore subjecting them to a shading treatment (20% shading) or a heavy fertilizing treatment (5 times dosage), the authors examined the combined effects of these factors on the characteristics of seedlings. 1) The plant height, top dry-matter, root dry matter, T·R ratio and the ratio of top dry-matter to plant height are more strongly influenced by the water-temperature than by air-temperature, except in the case of air-temperature 16°C, and the highest or near highest value of each character above mentioned is obtained under the condition of air-temperature 31°C combined with water-temperature 31°C. 2) The plant age in leaves advances slower at air-temperature 16°C than other-temperatures, and there are little differences in the progress of plant age among the treatments of air-temperature 21°C, 31°C and 36°C, while it advances progressively faster as the water-temperature goes up. 3) The percentage of decayed roots is strongly influenced by the water-temperature, not by the air-temperature, and it becomes higher without exception as the water-temperature goes up. This fact suggests the importance of controlling water-temperature in raising healthy seedlings. 4) As the air-temperature goes up, nitrogen content as well as carbohydrate content progressively decreased. This fact also suggests that the low air-temperature serves for raising good and healthy seedlings. 5) The shading treatment has a detrimental effect on every character investigated (except plant height) in all conditions, except at the air-temperature 16°C and the water-temperature 16°C. This fact suggests the importance of exposing seedlings to sunlight as much as possible for raising and healthy seedlings. 6) Heavy fertilization has a good effect on the most characters investigated, in particular on the ratio of top dry-matter to plant height. This fact also suggests the importance of studying heavy fertilization in seedling period.

[学科分类] 农业科学（综合）