Relevance and methodology. In order to determine the effect of increasing the proportion of far red light (different ratio of red and far red light) in the total spectrum of polychrome irradiation on the growth rates of sugar beet plants of the Smena hybrid, they were grown for 82 days under LED lighting under controlled climate conditions in a Synergotron digital device of the ISR 2.01 model with a twofold increase in the proportion of far red light compared to control.Results. An increase in the proportion of far red light led to an increase in the specific weight of leaves with a smaller area of leaves in the initial period of plant growth, higher values of the quantum yield of photosynthesis, the rate of electron transport, and a decrease in energy losses mainly to heat. The biometric indicators of plants changed depending on the period of ontogeny. In the initial period, the biomass of the aerial part prevailed, in the subsequent period, the biomass of root crops. In the experimental variant, the accumulation of biomass in the aerial parts of plants in the initial period of the experiment turned out to be less than in the control, and only at the end of the experiment was an excess of the total biomass in the experimental variant by 12.2%. There was an increase in the accumulation of root biomass compared to the control by 38.7%. The predominant part of the aboveground biomass of sugar beet was made up of leaf blades, the proportion of petioles was much less and practically did not depend on the composition of the light. At the end of the growing period, the dry matter content in root crops increased by 2.44% compared to the control, sugar content – by 0.65%. The data obtained can be used in the development of technology for artificial lighting of sugar beets when grown in closed agrobiotechnosystems in order to increase the yield and sugar content of root crops.

Relevance and methodology. In order to determine the effect of near-ultraviolet radiation with a wavelength of 380 nm on the growth and development of a sugar beet hybrid plant, Smena was grown for 82 days under LED lighting with phytolamps and under conditions of increased UV-A intensity of the light range (an increase in the UV/PPFD ratio (0.027) compared with the control (0.0075) while maintaining the ratio of the remaining sites spectrum). The study was carried out on the basis of the digital software package "Synergotron" with a controlled internal environment.Results. An increase in the share of UV-A in the illumination spectrum leads to a significant change in the biometric indicators of plants – the aboveground biomass increases by 2.2 times compared to the control, and the mass of the underground part (root crops), on the contrary, decreases by 86.9%. At the same time, the share of root crops in the total biomass of plants decreases from 60% in the control to 30%. The morphological structure of the leaf apparatus changes: the proportion of petioles increases significantly compared to leaf blades (64.8% of petioles in aboveground biomass, whereas in the control 30%). Probably, an increase in the share of UV-A in the spectrum can favorably affect the cultivation of leaf forms of beets and other root crops. UV-A radiation leads to a change in the chemical composition of root crops, in particular, a decrease in the accumulation of dry substances (by 1.58%) and a decrease in sugar content (by 1.8%). An increase in the proportion of UV-A in the irradiation spectrum changes the parameters of chlorophyll fluorescence and contributes to an increase in the maximum quantum yield of Fv/Fm, non-photosynthetic quenching of NPQ fluorescence and a decrease in the real quantum yield of photosynthesis Y(II), as well as the electron transport rate (ETR).