SOMATIC MUTATION RATE IN TRADESCANTIA STAMEN HAIRS AT LOW RADIATION LEVELS: FINDING OF LOW DOUBLING DOSES OF MUTATIONS
1972 年 47 巻 6 号 p. 411-421
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1972 年 47 巻 6 号 p. 411-421
Somatic mutation rates from blue to pink were studied in the stamen hairs of Tradescantia ohiensis KU 7 clone, a blue/pink heterozygote, exposed to 100 to 510mR/hr gamma rays or to 12mR/hr scattering radiation. The results obtained supported the previous finding of the sensitive genetic responses of this botanical system, demonstrating that the genetic effect could be detected with this system at a radiation level as low as 3.60R total exposure (also possibly only 0.96R) given at a low exposure rate of 12mR/hr. Pooling the present and previous data, a somatic mutation rate of 3.88 or 3.43×10-4 pink mutant events per hair per R was obtained for gamma-ray irradiation during hair development. The somatic mutation rate calculated for scattering radiation was even higher than this (1.25×10-3). The doubling dose of the somatic mutations at the specific locus was calculated to be 13.8 or 15.6R when irradiated with gamma rays during hair development, and the corresponding value with scattering radiation was 4.29R. Lower doubling doses could be calculated based on published data from the stamen hairs of the same and three other Tradescantia clones irradiated more acutely. These low doubling doses seem to throw doubt on the safety standards of radiations.
