Chromosome Structural changes in Tradescantia Microspores Produced by Absorbed Radiophosphorus

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Abstract
Cut T. paludosa inflorescences were inserted in various concentrations of radio-phosphorus (from 100 uc./ml. to 0.1 uc./ml.) for periods of 1 to 9 days. Cytological changes at the first post-meiotic (microspore) mitosis were counted. The types of aberrations resulting from B-radiation inside the plants were similar to those caused by x-rays and neutrons. Chromatid and iso-chromatid breaks behave as one-hit types. Their frequency shows an increase with time and correlates with the increase in radioactivity measured with an electroscope. Chromatid aberrations were observed within 24 hours and remained the principle type. Chromatid exchanges occurred with a relatively high frequency. Chromosome breaks were not observed until the 4th day. At the highest concentration (100 uc./ml.) the frequency of one-hit chromatid aberration types after 24 hours was equivalent to that produced by about 40 r of x-rays, and the very high breakage rate prevented aberration frequency counts after about 48 hrs.

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