Variation of spontaneous mutation frequency in Tradescantia stamen hairs under natural and controlled environmental conditions

Somatic mutation frequency in the stamen hairs of Tradescantia KU 7 and KU 9 clones exposed to low-level gamma rays.

“…The average temperatures listed are those of 12 days before the scoring periods, since the KU 7 stamen hairs show their maximum development thus are most affected by environmental factors about 12 days before flowering (Ichikawa 1970;Takahashi and Ichikawa 1976). It is obvious in this table that higher spontaneous mutation frequencies were obtained when temperature was lower.…”

“…(= T. reflexa Raf.) has been described to be a tetraploid (Ichikawa 1970(Ichikawa , 1971(Ichikawa ,1972b(Ichikawa , 1974Takahashi and Ichikawa 1976) but is noted here as a triploid, since our recent chromosome counts on the stock plants as well as on the materials used in the present and other studies have proved that all of those examined cytologically have 18 chromosomes (Ichikawa 1981a). The morphological characteristics, of this clone are, however, essentially unchanged from those described earlier (Ichikawa 1970(Ichikawa , 1974.…”

“…The mutation frequency ~ in the stamen shows a lower spontaneous mutation frequency than KU 7; see Takahashi and Ichikawa 1976). Insufficient data could be collected from plants irradiated with 2.9 and 6.4 R gamma rays, because those plants were damaged on the way to take them back to Kyoto.…”

“…The number of pink mutant events per 103 hairs in the control (or non-irradiated) plants placed in the control field of the Institute of Radiation Breeding varied from 4.95 ± 0.66 to 9.11 ± 1.31 in the present study and from 4.91 ± 1.41 to 6.87 ± 1.21 in earlier studies (Ichikawa 1971(Ichikawa , 1972b(Ichikawa , 1973 as listed in Table 5. Since the main cause of the variation of spontaneous mutation frequency in Tradescantia stamen hairs has been proved to be attributable to temperature variation (Takahashi and Ichikawa 1976;Yamashita 1976), i.e., the mutation frequency being inversely correlated to temperature, it is necessary to examine if the variation of spontaneous mutation frequency observed in the series of experiments at Ohmiya can be also attributable to different temperatures.…”

“…In particular, the characteristics of Tradescantia stamen-hair system, that is, the capability of detecting all pink mutant cells easily without being concealed by other cells as well as the relative easiness of handling a great number of samples, have proved to be especially suitable for studying the genetic effect of low-level radiations (Underbrink et al 1973;Ichikawa 1974Ichikawa , 1976Ichikawa ,1981b.…”