Influence of radiation exposure rate on somatic mutation frequency and loss of reproductive integrity in tradescantia stamen hairs

Abstract

Inflorescences of Tradescantia clone 02 (2 n = 12), hetero- or hemi-zygous for flower color, were exposed to a series of γ-ray exposures at two different exposure rates, 29.3 R/min and 0.026–0.52 R/min. Pink mutation-response curves, and survival curves based on reproductive integrity, were constructed for each of the exposure rates. Loss of reproductive intergrity was also assessed at high (256 R/min) and low (0.52–4.17 R/min) γ-ray exposure rates in T. blossfeldiana (2 n = 72). All observations were made on stamen hairs. The higher exposure rate was 1.3–1.7 times more effective in inducing pink mutations in clone 02. A greater efficiency of the higher exposure rate was also found for both taxa at the loss of reproductive integrity endpoint. The D 0 values obtained at the higher exposure rates, 154 R for clone 02 and 720 R for T. blossfeldiana, were significantly lower than the corresponding values of 270 R and 1880 R obtained at the lower exposure rates. These D 0's differ by factors of 1.75 and 2.61 for clone 02 and T. blossfeldiana, respectively. D 0's for the two taxa were found to be inversely correlated with their interphase chromosome volumes.