Analysis of Developmental Factors Determining Yield and Its Application to Yield Prediction and Culture Improvement of Lowland Rice. : XLV. Effects of temperature and its daily range in different growth-stages upon the growth, grain yield and its constitutional factors in rice plants.

[摘要] Responses of the growth grain-yield and yield-constitutional factors to the temperature and its daily range were examined by subjecting rice-plants to different combinations of controlled day and night temperatures for 15 days in different growth stages. Optimum day and night temperatures for increasing the grain-yield and its constitutional factors and for advancing the date of heading were pointed out in different growth-stages, as shown in Table 1, while the optimum ranges of daily temperature could hardly be found. Some supplementary explanations are given as follows. (1) A high day temperature (36°C) and a low night temperature (16°C) are favourable for branching out of tillers, while a high day and night temperature (31°C) is suitable for development of tillers. Consequently, the day temperature of 31°C and the night temperature of 21°C have been found to be optimum for increasing the number of panicles. (2) A high day temperature is favourable for vigorous differentiation of spikelets and rachis branches, while the night temperature seems to have a much smaller effect on it than the day temperature. (3) A high day temperature (36°C) and a little low night temperature (21°C) are optimal for preventing the regeneration of spikelets and rachis branches. (4) Optimum day and night temperatures for ripening of grains are almost the same as those reported in the previous paper (Vol. XXV. No.4). (5) It is worthy of notice that a rather low night temperature in every stage of growth is necessary for favourable grain production, except the tillering stage and the late ripening stage. (6) It is also of great interest that the date of heading is clearly advanced by a low night temperature (16°C) at the tillering stage.

[学科分类] 农业科学（综合）