Efficient dry matter production at the vegetative stage because of low maintenance respiration rate among rice varieties

To clarify the effect of varietal differences in the maintenance respiration rate on dry matter production at the vegetative stage in rice, the maintenance respiration rates of the top of the plant in 26 rice varieties were investigated by the starvation method. The relationship between the dry matter increase and the dark respiration rate under natural conditions was also examined between four varieties with a low rate of maintenance respiration (Tainou 67, Esoshimamochi, Binato and Mangasa) and those with a high rate (Bouzu, Dular, Mangetsumochi and Alborio). A varietal difference was found in the maintenance respiration rate of the top and was not related to the nitrogen content of the top. Under natural conditions, the large dark respiration in the varieties with high-maintenance rates was not due to large growth respiration, but to large maintenance respiration. The gross photosynthetic rate of the low-respiration varieties was lower than that of the high-respiration ones, although the net photosynthetic rate of the low-respiration varieties was higher than that of the high-respiration ones because of differences in the maintenance respiration rate, which corresponds to 5% of gross photosynthesis. This study showed that the starvation method was useful for the selection of rice varieties with low-maintenance respiration rates. The effect of the varietal difference of the maintenance respiration rate in the vegetative stage on dry matter production was shown quantitatively.