[en] Research on this project has had as a major goal a combined ecologic-genetic investigation of somatic mutations in order to evaluate the impacts of certain changing environmental parameters. The ultimate aim, to better understand how such environmental-mutation interactions operate and to assure the information obtained be extrapolatable to conditions and events in nature. Higher plants delineate reproductive tissues late in development from meristematic, somatic tissues. Moreover, the prevailing method of reproduction may be without sexual fusion of gametes and/or wholly asexual (vegetative). Therefore, somatic mutations can have as far-reaching genetic significance for a plant population as when germ cells, themselves, are directly affected. Our data show diurnal temperature differences (DTD) of greater than or equal to 22.2 C-degrees to be very effective mutagenic agents in the Tradescantia somatic mutation system. Further, these ranges of DTD were found to occur often in important seed production areas. A DTD of 22.2 in magnitude can increase mutations 10-fold. And, durations short as 1-day can induce significant increases in mutation rate. Whether interaction of 22.2 DTD with low-level radiation (800 mR/day) is synergistic or attenuative is still debatable. We believe, however, that spontaneous, and 22.2 DTD induced, mutations occur mainly via the genetic mechanism of somatic crossing-over; mutations from acute ionizing radiation (e.g., 30-60 R γ) via chromosome breakage, producing micronuclei. Requirements for maximizing the Discriminatory Response Capability (DRC) in the Tradescantia somatic mutation system are set forth