A Study of Factors Affecting X-Ray-Induced Chromosome Aberrations in the Microspores of Tradescantia paludosa: I. Fractionation of Dosage in Helium, Air, and Oxygen

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Abstract
The microspores of T. paludosa were irradiated with two equal doses of 200 r separated by 0 to 10 hourly increments between doses. Temperature during irradiation and post-irradiation was maintained at 30[degree] C [plus or minus] 0.5[degree] and irradiated inflorescences were kept under continuous illumination until slides were made. Damage produced by the first irradiation remained available for interaction with effects of the second irradiation for at least 7 hours in atmospheres of He, for at least 9 hours in air, and for at least 10 hours in pure O2. Those irradiations performed in air exhibited a cyclic rise and fall in the aberration frequencies produced with increasing hourly increments between administration of the two doses. This phenomenon may furnish a basis for understanding the discrepancies between the results of other investigators using this same material. Hourly increments between fractions were not used by these workers, and consequently these variations would not be obtained.