SYNERGISMS DETECTED AMONG METHYL METHANESULFONATE, ETHYL METHANESULFONATE AND X-RAYS IN INDUCING SOMATIC MUTATIONS IN THE STAMEN HAIRS OF TRADESCANTIA CLONE BNL-4430

Synergisms among methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS) and X-rays in inducing somatic mutations were examined in the s tamen hairs of Tradescantia clone BNL 4430, a blue-pink heterozygote. The young inflorescence-bearing shoots with roots cultivated in the nu trient solution circulating growth th chamber were used as tester plan ts. The mutagenicity of each single mutagen, MMS, EMS or X-rays, was f irst examined and a dose-response relation for each of them was determ ined. Induced somatic pink mutation frequency per hair-cell division i ncreased with increasing MMS, EMS and X-ray doses, with slopes of 1.28 3, 1.293 and 1.252, respectively, on log-log graphs, confirming the ex istence of similar patterns of the three dose-response curves. MMS was found, however, to be approximately 20 times more mutagenic than EMS. As for synergism among the different mutagens, it was judged to be ac ting synergistically when an observed mutation frequency after applyin g two different mutagens was statistically significantly higher than t he mutation frequency expected from the additive effects of the two mu tagens. Clear synergistic effects in inducing mutations were confirmed between MMS and X-rays, EMS and X-rays, and also between MMS and EMS, mostly in the higher dose ranges of these mutagens. Synergistic effec ts in causing loss of reproductive integrity of hair cells were also o bserved among these three mutagens.