Green and far-red light: key acclimation factors that boost plant growth

The use of LED technology in controlled environment agriculture has enabled precise control over the light spectra provided to plants. Initially, lighting strategies focused mainly on red and blue (RB) wavelengths, while green (G) and far-red (Fr) light were excluded to reduce energy consumption. However, recent research has shown that G and Fr light contribute significantly to plant development, morphology, and photosynthesis. This study examined the effects of supplementing traditional RB lighting with G and Fr light on Lactuca sativa, focusing on both morphological and physiological acclimation. Various light treatments were tested under both continuous and discontinuous spectra. Photosynthetic performance was assessed using chlorophyll fluorescence and gas exchange techniques, while biochemical analyses provided insights into the composition of the photosynthetic apparatus. After two weeks of exposure, plants grown under light that included G and Fr wavelengths accumulated over 30% more biomass than those grown under RB light alone. Interestingly, RB light triggered a typical high-light-like response—increasing photosynthesis and electron transport—but also resulted in thicker leaves and a lower shoot/root ratio, increasing the metabolic cost of growth. In contrast, G and Fr light induced a low-light-like acclimation, promoting leaf expansion and ultimately enhancing plant growth. Our findings suggest that incorporating G and Fr wavelengths into LED lighting systems can improve plant growth efficiency, helping to meet the demands of modern indoor agriculture.