The Influence of Heat Treatments.on the Injury -4nd Cytogenetic Effects

N favorable material, effects of ionizing radiations may be measured in I terms of injury symptoms, cytological aberrations, and mutations. Usually these effects are associated with dosage, and increase or decrease together, i.e., they are correlated. However, in earlier experiments in which it was shown that a heat treatment either before or after X-radiation modified the results of the irradiation, there was a suggestion that these criteria were not necessarily correlated. The present investigatioii was designed to test whether or not it is a fact that under certain conditions the injury, chromosomal aberrations, and inutations resulting from x-radiation may not be correlated. The data reported herein show conclusively that injury symptoms can be iiiore or less divorced from genetic changes when X-rayed barley seeds are treated with heat either before or after the irradiation. Further, they show that a positive correlation does not necessarily exist between the mutation frequency and the frequency of chroinosodal aberrations.