SURVIVAL CURVES OF HAPLOID AND DIPLOID CHLAMYDOMONAS REINHARDTII EXPOSED TO RADIATIONS OF DIFFERENT LET

Haploid and diploid cell stages of the unicellular green alga Chlamydomonas reinhardtii were exposed to acute and fractionated doses of radiations, having LET values up to 1298 MeV g-1 cm2. The shoulder region of the acute survival curves was smaller the higher the LET, the reduction being greater for the diploid than for the haploid. In no instance did the response become exponential. Recovery on dose fractionation occurred at all LET's, and the magnitude of the recovery was correlated with the size of the shoulder. The survival data were fitted better by the multi-hit single target and Haynes repair models than by the single-target single-hit or multi-target single-hit models, but there were difficulties in the application of both the first two models to provide adequate biophysical interpretations of the phenomena. © 1969 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.