<p>The Allium test system is worldwide used for biological monitoring of environmental pollutants. We have studied toxic and mutagenic activity of water from the Chumysh River, which is one of the largest tributaries of the Upper Ob. Water samples were taken near industrial settlement Talmenka (Altai Territory of Russia) during the spring flood and low autumn water level in 2015. Root tips of <em>Allium cepa</em> L. was used as a biological model. There were examined 30 samples. Purified tap water of medium hardness served as a control sample. After the synchronizing the cell divisions, the onion bulbs with roots reaching a length of 2-3 mm were transferred to glass cups containing the selected samples of River water and cultured for several days at a temperature of +24 ± 1°C. After exposure, root tips were rinsed in distilled water and fixed in a cold mixture of ethanol and acetic acid (3:1). Fixed samples were used after 12-24 h or transferred to 70% alcohol and stored in refrigerator at a temperature of +4°C until required. The fixed materials were hydrolyzed in 1N HCl at 60°C for 5-8 min and squashed in aceto-orcein.<strong> </strong>Prepared slides were viewed under the microscope at a magnification of ×90.<strong> </strong>The mitotic index (MI), the phase indices, the frequency of abnormal mitosis, and chromosomal aberrations were determined by the examination of 500 cells per a replicate (100 cells per slide). We established that the decreased or increased levels of mitotic activity and the frequencies of pathological mitoses (up to 7.9%, P < 0.05) in onion root tips revealed the presence of mitotoxic and genotoxic agents in the Chumysh River water. We found that the most number of chromosomal abnormalities occurs at the stages of meta- or anaphase. The main abnormalities are chromosome laggings in meta- and anaphase, chromosome bridges, chromosome fragments and micronuclei. Their number increased in 5.0-10.8 times compared with the control value. It has been discovered the temporal and spatial distribution of compounds with different toxicity and genotoxicity within a stream. The greatest level of mitotic depression and the highest frequency of chromosomal mutations were observed in the tissues of the onion root tips germinated on the samples collected in low autumn water. The mechanisms of plant adaptation to unfavorable environmental factors are discussed.</p>
THE USE OF BISMUTH AS AN ELECTRON STAIN FOR NUCLEIC ACIDS
