抄録
The present X-ray fractionation experiments with PMCs of Trillium kamtschaticum could indicate that two distinct types of chromosome breaks are induced by X-irradiation, as judging from the time periods until the onset of rejoining. One of them was the breaks of which rejoining begins immediately and is complete within about 1 minute, and another was those which do not initiate rejoining until 30 to 60 minutes after irradiation. The possibility that the former is the breaks of ionic nature and the latter is of covalent nature was discussed.
