Effects of ionizing radiation on nucleic acids during embryonic development—metabolism during embryogeny and at embryonic tissue level

Abstract

Observation was made of effects of X-irradiation on DNA and RNA metabolism by means of rates of 32P incorporation into the nucleic acids during barley embryogeny.Levels of disturbances in 32P incorporation rates into DNA caused by X-rays are correlated inversely with the periods of postirradiation and proportionally related to tissue heterogeneity at the time of X-irradiation with the exception of the oldest embryos. Changes in 32P labelling of RNA induced by X-rays during barley embryonic development, however, are independent of the postirradiation periods and differences in the tissue heterogeneity. The levels of differences due to X-rays in 32P incorporation rates into the DNA of the three different regions of a mature embryo reflect the degree of tissue heterogeneity within the embryos at the time of X-ray treatment. Disturbances in the rates of 32P incorporation into DNA are greatest in the root tissue and least in the scutellar region; the shoot part is rated between the levels of the two tissue regions. In contrast, responses of 32P labelling rates of RNA to X-rays in the three different parts of a mature embryo are found to be independent of the tissue heterogeneity at the time of X-ray treatment and the postirradiation period during embryogeny.