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The share of UVB spectrum range (290-320 nm) in the solar radiation flux accounts for an average of about 1.5% of the radiant flux on the planet. Taking into account the fact that plants adapt to living conditions in the course of evolution, it can be assumed that the flow of UVB radiation is also used by plants, but at the level of subdoses that reach the Earth's surface. The aim of current work is to study the growth and development of spring wheat (“Irgina” cultivar) when treated with subdoses of UVB radiation. For processing, XeCl-excilamp (High Current Electronic Institute SB RAS) radiation was used. The spectrum of this lamp is a narrow band with a maximum at a wavelength of 308 nm, which corresponds well to the UVB range. In the course of study, the pre-sowing UVB radiation dose values for seeds were found, under the influence of which wheat sprouts had an increase in such indicators as the length and dry weight of the root, the length of the leaf and the ratio of the root/shoot masses. It was shown, that as plants developed, the nitrogen balance index was always higher in the experiment with radiation in plants whose seeds were subjected to pre-sowing treatment with UVB radiation. This indicates the activation of growth and development processes in plants, as well as the accelerated absorption and assimilation of nitrogen compounds. Under the action of dose 0.5 J/cm2 the weighting parameters grain productivity such as weight of grains per ear, spike weight, weight of 1000 pcs seeds and the grain yield exceeded the check by 10.2%. The UVB processing did not affect the quality of the wheat grain. Based on the obtained data, it is concluded that the use of XeCl-excilamp UVB radiation for pre-sowing stimulation of wheat is promising.

Atmospheric pressure plasma jets generated by apokamp discharge (APPJ AD) in ambient air was investigated for the improvement of growth parameters of spring wheat seeds («Irgina» cultivar) and for inhibition of potentially phytopathogenic fungi on seeds surface. In case of APPJ AD, active forms of oxygen and nitrogen (as well as the radiation of molecules) are formed in the air of atmospheric pressure, which increases their concentration in the streamer head by orders of magnitude, compared to traditional APPJ based on inert gases. Owing to this, we believe to concentrate action of active forms of oxygen and nitrogen in situ, on the biological target. In our case, this can intensify the processes of inactivation of microscopic mold fungi on the surface of seeds. We tested our hypothesis on wheat seeds infected with helminthosporiosis ( Bipolaris sorokiniana Shoemaker ) with a degree of infection of 50% and early blight ( Alternaria sp. ), whose infection rate was 10%. In the first case, the seeds were treated by apokamp plasma for 1 and 10 minutes. It provided a significant reduction in the degree of infection of seeds with helminthosporiosis by 1.7 and 2.3 times. In comparison with check variant, the treated seeds maintained high rates of viability and germination energy. In the second case, it was possible to completely inactivate alternariosis pathogens within 3 min of treatment. In addition, it is shown that the action of APPJ AD caused a statistically valid elongation of the roots of wheat seedlings. A hypothesis is proposed to explain the found effects. The potential advantages of APPJ AD in the task of seed surface treatment in comparison with other known atmospheric plasma techniques are discussed.