The Effect of Additional Night and Pre-Harvest Blue and Red LEDs and White Lighting During the Day on the Morphophysiological and Biochemical Traits of Basil Varieties (Ocimum basilicum L.) Under Hydroponic Conditions

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The effect of white and additional red and blue LED lighting at night (Blue-NLL, Red-NLL) and during the pre-harvest period (Blue-P-hLL, Red-P-hLL) on morphological and physiological parameters, elemental composition, content of polyphenols, and essential oils of purple basil cultivars ‘Ararat’ and green basil ‘Tonus’ grown in the hydroponic conditions of the climatic chamber was studied. The height of the plants was determined by the variety and the LED irradiation period. The highest purple basil plants were obtained in the variant with Blue-NLL illumination; the highest green basil plants were obtained under Blue-P-hLL and Red-P-hLL. The red spectrum, regardless of the lighting period and variety, increased the area and number of leaves, biomass, and vegetative productivity. Significant changes in the elemental composition of the vegetative mass of basil varieties were determined by the period of exposure to the red spectrum. Red-P-hLL stimulated the absorption and accumulation of Mg, Ca, S, and P from the nutrient solution, and Red-P-hLL reduced the nitrate content by more than 30.00%. Blue-NLL lighting increased the content of quercetin, rosmarinic acid, and essential oil and reduced the nitrate content in the vegetative mass by more than 40.00%. The effectiveness of the white LED was observed in increasing the vegetative mass of ‘Tonus’. The results of this study will be in demand in the real sector of the economy when improving resource-saving technologies for growing environmentally friendly leafy vegetable crops with improved chemical composition and high vegetative productivity.