The Effects of Carbon Dioxide on the Frequency of X-Ray Induced Chromosome Aberrations in Tradescantia

Abstract

Inflorescences of T. paludosa were enclosed in air-filled lucite chambers, then compressed to the desired pressure with CO2 or the control gas (N2 and/or air), so that the sealed chambers contained 1 atmosphere of air plus a positive pressure of the exptl. gas. After compression the sealed chambers were kept at 25[degree]C in the dark for 1 hr., then placed in the X-ray machine and exposed to 40 r/min. for 10 min. at room temp. in subdued light. After exposure the chambers were decompressed slowly for 30 min., then opened to air. Cytological examinations for chromosomal aberrations (dicentric and centric rings) were made 5 days after irradiation. The results indicated that exposure to CO2 without irradiation gave no chromosomal aberrations, whereas exposure to CO2 during irradiation increased the frequency of aberrations over that produced by irradiation in N2 and/or air. The aberration frequency increased with an increase in CO2 concn., ranging from 8.6% for .005 atmospheres of CO2 to 30.5% for 1.33 atmospheres of CO2. It is believed that CO2 tension is important in conditioning the response of chromosomes to irradiation.