抄録
We have discovered that some of the seeds lost their viability in the process of dormancy awakening. Following facts were found concerning this phenomenon. Dead seeds were found after one month from the beginning of dormancy awakening (either primary or secondary) in the storage within the soil under upland condition (70 to 80 per cent. soil moisture content of field capacity) at low temperature below 10°C (especially 10°C). Dead seeds did not differ from fresh seeds in the morphological appearance of the embryo at earlier time, but its dehydrogenase activity was missing. However, occurrence of dead seeds in the soil varied acording to the temperature and moisture content of the soil. In the storage under any moisture content of the soil at germination temperature and under submerged or air-dry condition at low temperature, dead seeds were not found. In well-drained paddy fields (submerged condition in rice season, upland condition after rice season), numbers of viable seeds decreased very rapidly during from winter to early spring. In poor-drained paddy fields (submerged condition in the whole year), numbers of viable seeds decreased very slowly because the seeds hardly died in the process of dormancy awakenig in winter. Accordingly, it was well established that longevity of seeds of barnyard grass are longer in poor-drained paddy fields than in well-drained paddy fields.
