The article presents the results of the analysis of sugar beet seedlings whose seeds were encrusted before sowing with protective-stimulating compositions (PSC) based on polyvinyl acetate dispersion (PVA) containing either brassinolide (BL, PSC-BL) or epibrassinolide (EBL, PSC-EBL) at a concentration of 10–8 M. Growth parameters, photosynthetic pigment content, and photosynthetic activity of plants were studied. It was found that seed treatment with PSC-EBL provided an increase in the root mass of seedlings by 56 % relative to the control. Using PAM-fluorimetry, it was revealed that PSC-BL reduces unregulated energy losses of photosystem (PS) II (Y(NO)) by 24 % and increased the efficiency of PS II (Y(II)) by 62 %.

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