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Aim. Estimation of the mass of dry matter of the stem of the main shoots of different varieties of winter wheat in the phases of flowering and full ripeness as a criterion for the grain productivity of its ear in years with different meteorological conditions. Methods. Field, morphometric, mathematical and statistical. Results. The mass of dry matter of the stem of the main shoots of winter wheat varieties was studied in years that differed significantly in weather conditions in the flowering phase and at full grain maturity. It was established that the mass of dry matter of the stem of the main shoot at the flowering and the full grain maturity varied significantly, respectively 0.6–1.2 g and 0.5–1.0 g in 2014, and 1.0–2.0 g and 0.8–1.5 g in 2016 depending on the variety, and under different growing conditions. Limits of variation of grain yield of the ear in 2014, ranged from 0.9 to 2.2 g and from 1.5 to 2.5 g in 2016. It was established that at the flowering, the correlation between the mass of grain from the head and the mass of the dry substance of the stem was significant at 99 % probability under growing conditions (r = 0.8–0.9). Conclusions. It is shown that grain productivity of main shoot in winter wheat is related to the ability of its stem to store assimilates during the vegetative period. It was established that the mass of the dry matter of the stem of the main shoots in the flowering phase can serve as a criterion for assessing its grain productivity. Keywords: Triticum aestivum L., mass of stem, grain yield.

Aim. A study of the effects of growth regulators derived from natural raw materials on the photosynthetic apparatus surface and the yield of winter wheat. Methods. Morphometric, spectrophotometric, statistical. Results. An increase in the value of canopy chlorophyll index (ChlI) of Smuhlianka and Astarta varieties under the treatment of plants with Stimpo growth stimulator was established at anthesis, a positive effect of the regulator Regoplant – only for Smuhlianka variety at milk-wax ripeness. Chlorophyll photosynthetic potential (ChlP) during the period anthesis – milk-wax ripeness increased significantly under the use of growth regulators in both varieties, while the efficiency of treatments had varietal differences: growth was greater (11–18% compared to control) in the variety Smuhlianka than in the variety Astarta (6–7%). A positive correlation was established between the yield and ChlP during the period anthesis – milk-wax ripeness. Under the action of treatment of plants with growth regulators, the increase in grain yield was significant (0.29–0.45 t/ha) only in the variety Smuhlianka. Conclusions. The positive effect of treatments of plants with growth regulators, obtained from natural raw materials, on the value of canopy ChlI at anthesis and ChlP during period anthesis – milk-wax ripeness was established. A positive correlation between the winter wheat yield and ChlP during the period anthesis – milk-wax ripeness was found. Varietal differences in the effect of growth regulators treatment of plants on ChlP and yield were found. Keywords: Triticum aestivum L., grain productivity, chlorophyll index, chlorophyll photosynthetic potential, growth regulator.