Adding Phyto-LED Spectrum to White-LED Light Increases the Productivity of Lettuce Plants

Abstract: The effect of light of various spectral compositions on the complex morphophysiological parameters of lettuce plants in hydroponic was studied. The light sources had the following light spectra: warm white light—2700 K, cold white light—6500 K, and Phyto-LED light, as well as 2700 K + Phyto-LED and 6500 K + Phyto-LED. The dry and fresh biomass, leaf area, stem length, photosynthetic pigment content, photosynthesis and transpiration rates, chlorophyll fluorescence parameters, and percentage of plants that passed into the generative stage of development were studied. The results showed that partial and complete replacement of white LEDs by Phyto-LEDs with lower green light content and greater amounts of far-red light in the radiation spectrum caused an increase in plant productivity of 37%, average leaf area, and transpiration rate in the treatments but also promoted an earlier transition of plants to flowering under light treatment, Phyto-LEDs, and Phyto-LEDs + white LEDs. The 2700 K + Phyto-LED treatment had one of the highest productivities, as did the Phyto-LED and 6500 K + Phyto-LED treatments, but this lighting treatment provoked less flowering on the 60th day of the growing period.