SECTORING PATTERNS OF SPONTANEOUS AND INDUCED SOMATIC PINK MUTATIONS IN THE STAMEN HAIRS AND PETALS OF MUTABLE AND STABLE CLONES OF TRADESCANTIA

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.