| Relation of radiation effects to dose rates of gamma-rays
in diploid wheat S. MATSUMURA and T. MABUCHI National Institute of Genetics, Misima, Japan In order to investigate the relation of radiation effects to dose rates, dry seeds of Triticum monococcum flavescens were irradiated by gamma-rays at 4-15 kr. For acute and chronic irradiation the dose rates, 10,000 r/hr with 137Cs and 35.6 r/hr with 60Co, were used, respectively. Chronic irradiation was slightly more effective in inhibiting seedling growth than the acute treatment applied at the beginning of the chronic, and was clearly less effective than that applied at the end of the latter. Also, acute irradiation showed clearly a higher chlorophyll mutation rate than the chronic did, which were terminated just before sowing. The later was the irradiation at the same dose, the more pronounced was the inhibition of seedling growth and the increase in chlorophyll mutations, especially at acute irradiation. Thus, almost no intensification of radiation damage due to storage effects was found, as already reported in Annual Report of National Institute of Genetics, No. 13: 97-99. A series of similar experiments with the same material was initiated to verify the earlier studies. Dry seeds were exposed to gamma-rays at the dose rates, 10,000 r/hr with 137Cs and 26 r/hr with 60Co, respectively. In general chronic irradiation was more effective in inhibiting seedling growth and increasing chlorophyll mutations than the acute treatment, applied at the end of the chronic, especially at high dose (15 kr). It is supposed, against the earlier studies, that a slight intensification of radiation damage due to storage effects was involved. |