[en] RRRecognition of potential genetic hazards from exposing the earth's biota to ionizing radiation has led to this being an intensively studied environmental stress. Yet the possibility that other environmental components might alone, or through interactions with radiation or one another, produce sufficient modulation of mutation frequency to be of genetic consequence to natural ecosystems remains largely ignored. Delineation of germinal tissue in plants, unlike animals, is often delayed until late in development, and the prevailing mode of reproduction may involve cells other than typical gametes. Thus, environmental situations which appreciably alter production and accumulation of somatic mutations can have as significant an effect upon dispersion of mutations throughout a plant population as though mutations occurred in germ cells themselves. Combined ecologic-genetic investigations offer one of the best approaches for evaluating the impact of changing environment on genetic systems. As their experimental system in such research, the authors used somatic mutations occurring at the D-locus in flowers of Clone 02 Tradescantia-Capabilities for environmental modulation and the biological mechanisms whereby they are mediated were examined through manipulations of controlled environment, purposefully aimed at providing information which will be reasonably extrapolatable to conditions in nature. Results presented describe the high degree to which somatic mutations can be modulated by a naturally occurring environmental parameter and large diurnal temperature difference. Relationships with ionizing radiation regarding interactions and genetic mechanisms are discussed. (author)