Konotop Y. Nitrogen in adaptive response of soybean (Glycine max (L.) Merr.) under cadmium treatment.

The thesis is devoted to the investigation of the role of nitrogen in adaptive response of soybean under cadmium treatment. Dose-dependent impact of nitrogen in the regulation of protective mechanisms to cadmium ions through the formation of induced resistance of soybean was revealed. It was found that low doses of nitrogen (30 kg/ha, 1,2 mM) induce the adaptive response of plants associated with preservation of homeostasis and maintenance of a stable content of photosynthetic pigments and SQDG in soybean leaves. Nutrition of soybean with 30 kg/ha of nitrogen showed 60% increasing of the total protein content and was favorable for high quality of seeds. High concentrations of nitrogen (180 kg/ha, 24 mM) lead to disturbances of homeostasis, as reflected by the increasing content of TBA-active products, reducing content of pigments and SQDG and productivity decreasing due to the appearance of protein fractions with low sulfur-containing amino acids in soybean seed. Accumulation of callose in the cells of rhizoderma and exoderma, that creates additional barrier to cadmium ions, was revealed. Structural changes were accompanied by activation of the protective enzyme catalase, which regulates redox homeostasis under cadmium and low doses of nitrogen application. Activation of the enzyme chitinase and change of its isoform composition by cadmium ions and different concentrations of nitrogen were admitted. Cadmium-specific isoforms (~25 and 30 kDa) of chitinase which revealed sensitivity to high concentration of nitrogen in the nutrient media were identified. Activity increasing of acidic and basic isoforms of chitinase indicates their metal-specific properties. Key words: Glycine max (L.) Merr., adaptive reactions, doses of nitrogen fertilizers, cadmium, lipid peroxidation, callose, chitinase.