著者

SADAO ICHIKAWA

出版者

日本遺伝学会

雑誌

遺伝学雑誌 (ISSN:0021504X)

巻号頁・発行日

vol.47, no.6, pp.411-421, 1972 (Released:2007-05-21)

参考文献数

12

被引用文献数

13 12

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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.

著者

Marie SANDA-KAMIGAWARA Michio TOMIYAMA Sadao ICHIKAWA

出版者

日本遺伝学会

雑誌

遺伝学雑誌 (ISSN:0021504X)

巻号頁・発行日

vol.70, no.3, pp.339-353, 1995 (Released:2004-06-24)

参考文献数

29

被引用文献数

8 10

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The sectoring patterns of spontaneous and radiation- and EMS-induced somatic pink mutations were analyzed in the stamen hairs and petals of Tradescantia clones heterozygous for flower color (blue/pink). Spontaneous pink mutations were analyzed using clone KU 20 (a highly mutable clone especially at lower temperature) grown outdoors and clones KU 27 and BNL 02 (stable clones) grown under controlled environmental conditions, while induced pink mutations were analyzed using clones KU 27 and BNL 02 grown under the controlled environments. As for spontaneous mutations in the stamen hairs, the ratio of the number of single interstitial pink mutant events against that of single terminal pink mutant events was somewhat larger than 1 in all the three clones examined, indicating that somewhat more interstitial pink mutant events occur spontaneously than terminal pink mutant events. After treatments with X rays, gamma rays or EMS, however, the ratio increased to about 3 in the two clones examined, showing much more frequent inductions of interstitial pink mutant events than terminal pink mutant events by these mutagens. The daily changes of the sectoring patterns of radiation- and EMS-induced terminal pink mutant events in the stamen hairs showed a good accordance with the pattern of the stamen-hair development. Multiple pink mutant sectors in the same hairs were observed at much higher frequencies than expected from independent occurrences, especially in cases of spontaneous mutations in the mutable clone and of radiation-induced mutations in the two stable clones, suggesting the involvement of somatic recombinations. The sectoring patterns of radiation- and EMS-induced somatic pink mutations in the petals also showed daily changes which reflected the pattern of the flower-petal development.

著者

SADAO ICHIKAWA ICHIZO NISHIYAMA

出版者

日本遺伝学会

雑誌

遺伝学雑誌 (ISSN:0021504X)

巻号頁・発行日

vol.42, no.3, pp.175-187, 1967 (Released:2007-05-21)

参考文献数

36

被引用文献数

2 2

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Dry seeds of a Japanese variety of common wheat (6x), Shinchunaga, were irradiated with 10 to 40 kR of gamma rays from 60Co. No chlorophyll mutations were detected, while various kinds of morphological mutants were found in the X2 through X8 generations. About one third of the morphological mutants were found in the X2, another third in the X3, and the remaining third in the later generations.The lack of any chlorophyll mutation and the frequent occurrence of various morphological mutations are considered to indicate that there is a difference in the extent of differentiation in this polyploid plant between essential genes such as those for chlorophyll production and non-essential genes such as those determining spike length or density.Many speltoid, compactoid, squareheaded, lax-spiked and dense-spiked mutants were found, as well as various other mutants. Cytogenetical investigations were performed on these morphological mutants, and it was found that most of these morphological mutants were caused by various chromosomal aberrations, such as deficiencies, telocentrics, isochromosomes, and various aneuploid constitutions.

著者

Sadao ICHIKAWA Chizu ISHII

出版者

日本遺伝学会

雑誌

遺伝学雑誌 (ISSN:0021504X)

巻号頁・発行日

vol.66, no.1, pp.27-40, 1991 (Released:2005-11-01)

参考文献数

29

被引用文献数

17 18

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Somatic pink mutation frequencies in the stamen hairs of Tradescantia BNL 02 clone grown for 76 days in two soil samples taken from the Bikini Island (where a hydrogen bomb explosion test had been conducted in 1954) were investigated. A significantly high mutation frequency (2.58±0.17 pink mutant events per 103 hairs or 1.34±0.09 pink mutant events per 104 hair-cell divisions) was observed for the plant grown in one of the two Bikini soil samples, as compared to the control plants (1.70±0.14 or 0.88±0.07, respectively) grown in the field soil of Saitama University. The soil sample which caused the significant increase in mutation frequency contained 6,880±330 mBq/g 137Cs, 62.5±4.4 mBq/g 60Co, and some other nuclides; a 150 μR/hr exposure rate being measured on the surface of the soil sample. The effective cumulative external exposures measured for the inflorescences of the plant grown in this soil sample averaged at most 60.8 mR, being too small to explain the significant elevation in mutation frequency observed. On the other hand, internal exposure due to uptake of radioactive nuclides was estimated to be 125 mrad (1.25 mGy) as an accumulated effective dose, mainly based on a gamma-spectrometrical analysis. However, it seemed highly likely that this value of internal exposure was a considerable underestimate, and the internal exposure was considered to be more significant than the external exposure.

著者

SADAO ICHIKAWA

出版者

日本遺伝学会

雑誌

遺伝学雑誌 (ISSN:0021504X)

巻号頁・発行日

vol.48, no.1, pp.35-40, 1973 (Released:2007-05-21)

参考文献数

6

被引用文献数

11 8

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Potted plants of Tradescantia ohiensis KU 7 clone (heterozygous for flower color) were exposed to 60Co gamma rays and/or scattering radiation in the gamma field of the National Institute of Radiation Breeding. Somatic mutation rates were scored in the stamen hairs for 16 days, and the genetic effects of direct gamma rays and scattering radiation were compared. Scattering radiation was proved to be about 27 or 25% more efficient in inducing somatic mutations than the direct gamma rays from 60Co source.