Effect of Temperature at the Ripening Period on Dark Respiration and Dry Matter Production in Rice. - Comparison of the effects in the plants sown in pots at different times

To examine the influence of temperature on the dark respiration and the dry-matter increase of the panicle of rice in the ripening period, we investigated the dark respiration rate and the dry matter production in the ripening period in the plants sown in pots at April, May, and June. The heading date was on August 4 in the plants sown in April, and it was delayed 14 and 28 days by sowing in May and June, respectively. The mean temperature from the 6th to 19th day after heading in the plants sown in April was 4°C higher than that in the plants sown in May and June. The growth and the maintenance respiration were estimated by using the regression method. The dark respiration of the panicle mainly contributed to the panicle growth respiration, and the maintenance respiration was higher in the plants sown in April and May than those sown in June. The dark respiration rate of leaf blade and stem was mainly related to the translocation rate of the carbohydrate to the panicle, and the maintenance respiration rate was low in the plants sown in June than in those sown in April or May. It was suggested that the rise of mean temperature did not necessarily increase the maintenance respiration and that the maintenance respiration was influenced not only by the temperature in the ripening period but also by the temperature before heading. It was also quantitatively shown that the dry matter production of the panicle was decreased by the increase in dark respiration accompanied by the increase in maintenance respiration.