Abstract
Variation of the specific rate of average night dark respiration (Rs-n) expressed as mgCO2 g dry wt. -1h-1 of individual plant was examined in semi-dwarf high-yielding indica, F1 hybrids and japonica cultivars grown in the field under favorable management to clarify the causal factors for the variation of the dark respiration rate in the later growth stage (from around heading to maturity) of rice. The Rs-n was the highest around heading stage and the Rs-n gradually decreased with the advance of growth stage in a quadratic manner. Besides, Rs-n was linearly related with both nitrogen content and solar radiation of sampling day. The correlation coefficient of the multiple regression analysis on the effect of these three factors on Rs-n was 0.831. Varietal difference in the dark respiration rate was not large. Particularly, little variation of the dark respiration rate of leaves was observed among materials used in spite of the remarkable difference in sugar content. Variation of Rs-n with different growth stage was mainly due to the change of weight ratio of the composing organs to the total dry weight and to the change of specific respiration rate of composing organs. The respiration rate per nitrogen (Rs N-1) of the leaf increased during ripening stage, while those of other organs decreased.
