Variation of spontaneous somatic mutation frequency in the stamen hairs of a mutable clone of Tradescantia, KU 20

Variation of spontaneous somatic pink mutation frequency was studied in the stamen hairs of Tradescantia KU 20 clone, a highly mutable blue/pink heterozygote. The spontaneous mutation frequency varied greatly from 4.03±1.21 to 120±7 and from 18.8±3.1 to 110±5 pink mutant events per 103 hairs when the plants were grown outdoors and in the greenhouse, respectively, being generally higher at lower temperature and also in the greenhouse than in outdoors. The spontaneous mutation frequency under controlled environmental conditions also varied from 3.06±0.37 to 40.8±3.1 pink mutant events per 103 hairs, showing a clearer negative correlation with temperature. It was found that the spontaneous mutation frequency under controlled environmental conditions increased when day/night temperature shifts were applied, especially with a 5°C shift than with 3°C shifts. The difference between the highest and the lowest mutation frequencies reached almost 40 times, and this clone was confirmed to be a temperature-sensitive mutable clone. A repair mechanism of DNA damages occurring spontaneously, which is more effective at higher temperature, thus presumably an enzymatic one, is very likely involved in the mutable nature of this clone.