One of the important indicators of the viability of plants is resistance to salt stress. Soil salinity not only lowers crop yields, but also negatively affects ornamental plants. Increasing the resistance of plants to salinity has both fundamental and practical significance. An important role in enhancing the adaptive potential of plants belongs to selenium. Selenium has antioxidant properties and is part of the structure of one of the main antioxidant enzymes, glutathione peroxidase. Unlike ionic forms of selenium, nanoparticles are less toxic, biologically available and have a prolonged action. However, the effect of selenium nanoparticles on plant resistance to salt stress has been poorly studied. The purpose of this work was to study the effect of selenium nanoparticles on the salt tolerance of annual flower crops. The morphology of the surface of a thin nanocomposite selenium film was studied by scanning atomic force microscopy (AFM). It is shown that the surface of a film is a cluster of nanoclusters consisting of nanograins. The average size of the nanograin is about 34 nm. The research subjects were the marigolds rejected (Tagetes patula L.) and elegant zinnia (Zinnia elegans Jacq.). Seeds were soaked for 4 h in water solutions of nanoselenium at a concentration of 5.0, 10.0, 20.0 and 30.0 mg L~(-1). Treated seeds of T. patula were germinated in Petri dishes in saline solutions (100 mM NaCl) for 7 days at 24℃. Z. elegans seeds were grown on a saline substrate (2.0 g kg~(-1) NaCl) in the vegetation vessels for 30 days at 24°C. Control served as: 1 - seeds soaked in distilled water; 2 -seeds soaked in distilled water, grown under conditions of salt stress. The protective effect of selenium nanoparticles on seed germination, the morphometric indices of plants (linear dimensions of roots and the aerial part, the mass of wet and dry matter), as well as the content of proline in the conditions of simulated chloride salinity are investigated. It is shown that the treatment of seeds T. patula and Z. elegans with nanoselenium increases seed germination, morphometric indices of plants and proline content in comparison with the control samples (without nanoselenium, NaCl). The maximum effect was obtained at the concentration of nanoselenium 10.0-20.0 mg L~(-1), and at 30.0 mg L~(-1), all the morphometric indices were reduced. Thus, the nanocomposite of selenium stabilized by sodium alginate at certain concentrations can activate the protective mechanisms of flower cultures under conditions of salt stress.
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