Relative Biological Effectiveness of 0·43-MeV and Lower Energy Neutrons on Somatic Aberrations and Hair-length in Tradescantia Stamen Hairs

Summary

Young influorescences of Tradescantia clone 02 were irradiated with 0·43-MeV neutrons at doses between 0·163 and 24·4 rads. In a similar experiment, influorescences were irradiated with neutrons of lower energy (nominally 80 keV) at doses between 4 and 128 rads. Data from these experiments were compared with data from 250-kVp x-rays at doses between 11·5 and 432 rads. In all three experiments, stamen hairs were scored daily from day 7 to day 16 after irradiation.

The characteristics of the dose-response curves are given for eight somatic aberrations: the colour change from blue to pink or to colourless in normal-sized cells, and the changes from the normal-sized blue cells to blue giant or blue dwarf cells, pink giant or pink dwarf cells, or colourless giant or colourless dwarf cells.

RBEs were found to decrease with increasing dose. The maximum RBE found was 166 for blue giant cells. However, RBEs for the other aberrant cell-types were about 20 to 30 for 0·43-MeV neutrons and about 10 for 80-keV neutrons. RBEs of about 10 and 6 were found for reduction of mean number of cells per stamen hair for 0·43-MeV and 80-keV neutrons, respectively. The data are discussed in terms of microdosimetric concepts.