Abstract
Previously, we reported that the temperature range for light-dependent germination of Rumex obtusifolius L. seeds was affected by the stage of seed development at harvesting. Especially, in later stage of the seed development in which the moisture content fell rapidly, the narrowing of the temperature range for germination occurred, indicating the establishment of seed dormancy. The present experiment was undertaken to make clear the changes in the germination capacity and the moisture content during air drying period immediately after harvesting at various stages of development and after-ripening of the seeds. The results obtained were as follows; 1) The seeds harvested on the 30th day from flowering were estimated to be at the beginning of the third phase of seed development as shown in the second report of this series. Immediately after harvesting, the moisture content of the seed was 60.7% and the germination occurred under continuous light condition at both 20℃ and 25℃. When the seeds were dried in air at room temperature after harvesting, however, the germination rapidly decreased only at 25℃ as the moisture content decreased. On the contrary, the time course of the germination at 20℃ was hastened corresponding with the length of air drying period. No germination under continuous dark condition regardless of temperature occurred at any stage of air drying period after harvesting. 2) The seeds harvested on the 21st day from flowering were estimated to be at the second phase of the seed development. The seeds showed a high germination percentage at both 20℃ and 25℃ under light condition immediately after harvest. During air drying period following the harvest, the germination at 25℃ under light condition hardly decreased in spite of the decrease of the moisture content. 3) Many of the seeds were hardly detached from the plant after maturing in field condition. The light-dependent germination of the seeds attaching to the plant occurred within a limited temperature range, that was 18℃-23℃, for about one month after maturing. But, with the lapse of the period of after-ripening in field condition, the range of the germination temperature gradually widened above 23℃. 4) Early in the after-ripening, the time course of the germination at 18℃ was hastened and a constant pattern was established. 5) Changes in the germination capacity and the moisture content of the seeds harvested at any stage of after-ripening were scarcely observed during air drying period following the harvest.
