The Frequency of X-Ray-Induced Chromatid Breaks in Tradescantia as Modified by Near Infrared Radiation

Abstract

Expts. are reported in which it has been shown that near infra-red radiation, when combined with x-rays, significantly increases the frequency of x-ray-induced breaks and rearrangements in the microspore chromosomes of Tradescantia. All types of detectable alterations are increased by pre-treatment, while post-treatment increases the frequency of single deletions and exchanges but does not increase the frequency of double deletions. A delay of 21 hrs. between pre-treatment with infra-red and x-rays does not appreciably decrease the effectiveness of infra-red, suggesting that the change induced by infra-red is of a relatively permanant nature. The nature of the effect of infra-red is poorly understood.