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.