Abstract
The influences of temperatures and gaseous conditions on dormancy and germination in rice seeds were investigated, in order to make clear the mechanism of seed dormancy.
1. In comparison of seed dormancy found in indica type and japonica type varieties, the number of varieties of indica type showing a high seed dormancy were more remarkable than that of japonica type.
2. The speed of activation of seed germination in non-dormant varieties was faster than that in dormant ones. This activation mentioned above seems to be related to germination percentage and magnification of temperature-extent, in which seeds of rice could germinate. Then, the activation of seed germination was recognized as showing varietal difference, but seed germination activated entirely was not recognized the varietal difference at 20°C-32°C.
3. Effects of alternating treatments of temperatures on the breaking dormancy of seeds were only recognized on plot alternated between 20°C and 32°C. High temperature treatment of seeds at 40°C immediately after sowing broke completely the seed dormancy, therefore it was considered that effect of high temperature treatment on the breaking of seed dormancy was not revealed by dryness of seeds, but was directly revealed by action of high temperature.
4. On the germination of dormant seeds, dormancy of fully ripened seeds was completely broken when seeds were placed in 100% oxgen tension, and the acceleration of germination percentage could be taken in high oxgen tension. Accordingly, it became clear that oxgen supply was requested on the germination of dormant seeds.
