Key factors enhancing growth by integrating green and far-red light in LED lamps

Indoor vertical farming relies on precise environmental control to optimize plant growth, with light being a key factor. The adoption of LED technology has improved energy efficiency, allowing precise control over light spectra and intensity. Traditionally, controlled environments primarily supplied red and blue (RB) wavelengths due to their high absorption by photosynthetic pigments, while green (G) and far-red (Fr) light were excluded to minimize energy costs. However, G and Fr light enhance plant growth by penetrating the canopy, stimulating photosynthesis of shaded leaves and triggering morphological responses through photoreceptor activity. Moreover, maximizing photosynthesis alone does not necessarily lead to greater biomass accumulation, raising the unresolved question of which key factors drive plant growth and how they interact. In this study, we explored how G and Fr light shape morphometric responses, photosynthetic and respiratory acclimation in Lactuca sativa. Building on previous research defining optimal RB ratios for vertical farming, we tested different intensities and proportions of G and Fr light under both discontinuous and continuous emission spectra. To evaluate photosynthetic performance, we conducted fluorimetry and gas exchange measurements, while biochemical assays provided insights into photosynthetic apparatus composition. Additionally, we analyzed morphometric traits related to relative growth rate (RGR) to assess the broader impact of light quality on plant growth. After just two weeks of acclimation, light spectra incorporating G and Fr wavelengths boosted biomass accumulation by over 30% compared to plants grown under RB light. RB light induced a high-light-like response, increasing net CO₂ assimilation and electron transport rate, whereas G and Fr light led to low-light-like acclimation, following an opposite trend. Morphological acclimation to RB light resulted in thicker leaves and a lower shoot/root ratio, increasing the carbon cost of leaf expansion. In contrast, G and Fr light induced the opposite trend, ultimately enhancing RGR. Our results highlight the need to integrate photosynthetic, morphological, and respiratory acclimation to optimize lighting strategies for indoor farming. Incorporating G and Fr wavelengths in LED systems enhances plant growth and resource efficiency to better meet modern agricultural demands. This work was funded by project “POC Plant Flow Solutions”, NODES Spoke 2, Green technologies and sustainable industries – CUP D17G22000150001.