[en] Relationship between gamma radiation sensitivity and morphological and physiological traits was studied in four rice varieties: Osaka-Asahi and Ginbozu (Japonica) and Jhona 349 and Magnolia (Indica). R D₅₀ values were almost double in Indica varieties than Japonica. The release of endogenous reducing sugar decreased with the increase in radiation dose and corresponded to the degree of morphological damage. It seems that the difference in radiosensitivity among these varieties, particularly between Indica and Japonica types, may be due to differences in sensitivity to gamma radiation in a release process including and/or activation of enzymes