VARIATION OF SPONTANEOUS SOMATIC MUTATION FREQUENCY IN THE STAMEN HAIRS OF TRADESCANTIA CLONE BNL-02

Variation of spontaneous somatic mutation frequency was studied in the stamen hairs of Tradescantia clone BNL 02 heterozygous for flower col or (blue/pink; the blue color being dominant), one of the most stable clones in terms of spontaneous mutation frequency. Young inflorescence -bearing potted plants of this clone were grown under several differen t controlled environmental conditions, and the spontaneous pink mutati on frequency in the stamen hairs was scored daily for three (partly tw o) weeks. The average number of hairs per stamen decreased as inflores cences became older, especially during the first one week or so after the inflorescences initiated flowering. The average number of cells pe r hair also decreased with the age of inflorescences, but the decrease s were much smaller than those in the number of hairs. On the other ha nd, the spontaneous mutation frequency expressed as the number of pink mutant events per 10(4) hair-cell divisions did not show any signific ant changes with the age of inflorescences. The spontaneous mutation f requency varied, however, depending on the controlled environmental co nditions and showing nearly significant negative and positive correlat ions with average temperature and diurnal temperature difference, resp ectively, although the variation observed was very much smaller than t hose reported earlier in a temperature-sensitive mutable clone KU 20 a nd also smaller than those in other clones.