Chromosomal Aberrations in Onion Roots from Plants Grown in an Atmosphere Containing C14O2 1

1. Sets of the Ebenezer variety of onion grown in the special nutriculture chamber at the Argonne National Laboratory under controlled temperature and humidity conditions had their natural atmospheric carbon dioxide supply supplemented by the addition of C14O2so that the total concentration varied from 0.03% to 0.1%. The photoperiod was extended to 16 hours by means of incandescent lamps. 2. One leaf from a plant of approximately a dozen grown showed a chlorophyll-deficient streak along its entire length. There were no chlorotic streaks in control plants. 3. Roots from the carbon 14 plants showed both chromosome and chromatid breaks and fragments in dividing cells, bridging, and micronuclei. No aberrancies were observed in dividing cells of control roots.