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 stamen hairs of Tradescantia clone BNL 4430, a blue-pink heterozygote. The young inflorescence-bearing shoots with roots cultivated in the nutrient solution circulating growth chamber were used as tester plants. The mutagenicity of each single mutagen, MMS, EMS or X-rays, was first examined and a dose-response relation for each of them was determined. Induced somatic pink mutation frequency per hair-cell division increased with increasing MMS, EMS and X-ray doses, with slopes of 1.283, 1.293 and 1.252, respectively, on log-log graphs, confirming the existence 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 acting synergistically when an observed mutation frequency after applying two different mutagens was statistically significantly higher than the mutation frequency expected from the additive effects of the two mutagens. 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 effects in causing loss of reproductive integrity of hair cells were also observed among these three mutagens.