PHOTOSYNTHESIS AND PRODUCTIVITY OF BASIL PLANTS ( <i>Ocimum basilicum</i> L.) UNDER DIFFERENT IRRADIATION
Improving the efficiency of growing plants in phytotrons is largely linked to the introduction of advanced technologies, providing the optimization of the light conditions. The use of modern light sources such as light emitting diodes (LEDs) or induction lamps can reduce the energy consumption for growing plants due to the high light output, long work and control of the spectrum of irradiation. Comparative studies of growth processes and activity of the photosynthetic apparatus of plants of Basil ( Ocimum basilicum L.) variety Ararat, when using LEDs and induction lamps with an energy capacity of 64 and 150 W, respectively were done. The light intensity was 80-85 µmol photons•m <sup>-2</sup>•s <sup>-1</sup> under LEDs white light and 240-260 µmol photons•m <sup>-2</sup>•s <sup>-1</sup> under induction lamps. CO <sub>2</sub> gas exchange, the content of pigments and growth processes in plants grown in hydroponic conditions were estimated. The rate of photosynthesis under induction lamp was more than 2 times higher than under LEDs (2.6±0.4 and 1.2±0.3 µmol CO <sub>2</sub>•m <sup>-2</sup>•s <sup>-1</sup>, respectively), although there was a slight decrease in the content of the chlorophylls (a + b) to 0.71±0.01 mg/g dry weigh compared to 0.83±0.03 for LEDs. More than twofold increase in the rate of photosynthesis did not result in the same increase in the accumulation of plant biomass that may be connected with different light saturation of growth processes and photosynthesis. The efficiency of biomass accumulation per 1 W of energy power for a period of 40 days under LEDs was 1.7 times higher than under the irradiation of induction lamp. Significant difference in photosynthetic efficiency was not detected. At elevated concentrations of CO <sub>2</sub> the rates of photosynthesis were comparable as a result of higher values of the quantum yield of photosynthesis, activity ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO) and the efficiency of carboxylation in LEDs plants. The investigation of structural and functional parameters of the photosynthetic apparatus and growth processes under the action of different light intensity showed the complex nature of the changes of some processes during long-term exposure to light of different intensity and spectral composition.