Abstract
Plant cells are known to be more radiation-tolerant than mammalian cells. To explore the mechanisms of the radiation tolerance, it is necessary to irradiate plant cells with heavy ions that have a high biological effectiveness. However, the random distribution of tracks had interfered to utilize it. Ion microbeam that can target individual cells exactly is a good way to settle this issue. In this study, we developed a system for irradiating heavy ion microbeam on tobacco protoplasts as a model of single plant cells.
Tobacco protoplasts were embedded in the agarose medium and inoculated into the custom-made sample holder, in which CR-39 is incorporated to detect ion traversals. The colony formation rate of unirradiated protoplasts in this holder was 22.7±6.7%. The cells were irradiated by collimated carbon ions with 20 μm in diameter. The ions that penetrated the sample were detected and counted by the scintillatior-photomultiplier assembly and pulse counter. After the irradiation, the ion tracks on CR-39 was visualized by alkaline treatment and the number of ion hits on the individual cells was scored. Hit rate of the carbon ions on the cells was about 60%. The colony formation rate of tobacco protoplasts was not reduced by the irradiation of 1 to 10 carbon ions.
