Using Different Modifications of the Allium Test to Evaluate Radiotoxicity of Bottom Sediments of the Yenisei River

Background. Bottom sediments (BS) of the Yenisei River contain xenobiotics of the chemical and radiation origins, which may adversely affect life functions of aquatic organisms. Previous assays of BS samples using the Allium test showed contradictory responses of the endpoints of onion bulbs (stimulation and inhibition) to the chemical and radionuclide composition of the BS. The Allium test with germinated seeds has not been used so far to test samples of the Yenisei BS, although previous studies showed sensitivity of this test object to exposure to low-dose gamma radiation. Purpose. The purpose of the study was to assess the possibility of using two modifications of the Allium test (A. cepa bulbs and seeds) to evaluate toxicity of samples of the Yenisei River BS containing relatively high activity concentrations of artificial radionuclides. Material and Methods. Toxicological laboratory experiments were conducted using three samples of the Yenisei BS containing high activity concentrations of the artificial radionuclide 137Cs; artificial BS prepared according to the standard protocol were used as the control. Activity concentrations of BS radionuclides were measured using a gamma-spectrometer coupled to a hyper-pure germanium detector (Canberra, U.S.). The test object was onion Allium cepa L. cv. Stuttgarter Riesen (bulbs and seeds). Root growth was chosen as the endpoint to determine BS toxicity. Results. Experiments with radioactive BS from the Yenisei River demonstrated significant stimulation of root growth in the modification with onion bulbs and inhibition of root growth in the modification with onion seeds. In previous research, stimulation of root growth was observed in onion bulbs exposed to Yenisei BS containing lower activity concentrations of 137Cs. For the first time, inhibition of root growth of onion seedlings was observed in assays with BS containing a wide range of 137Cs activity concentrations. Conclusion. Comparison of two modifications of the Allium test (bulbs and seeds) for assessing the toxicity of BS showed that only the growth of onion seedling roots used as an endpoint has sufficient sensitivity to the content of the artificial radionuclide 137Cs in BS and makes it possible to evaluate the biological effects of radioactivity. Funding. The study was funded by State Assignment of the Ministry of Science and Higher Education of the Russian Federation (project No. 0287-2021-0019).