Optimizing the LED Light Spectrum for Enhanced Seed Germination of Lettuce cv. ‘Lollo Bionda’ in Controlled-Environment Agriculture

Light is crucial in controlled-environment agriculture (CEA), affecting germination, growth, and overall plant quality. Here, we explored the optimization of various LED light spectra on the germination traits such as germination percentage, mean germination time, germination index, vigor index, and early seedling growth of ‘Lollo Bionda’ lettuce seedlings in a plant factory. A completely randomized design was implemented, involving three replications. LED lamps with different spectral compositions—red (R, peak at 656 nm), red/blue (3:1 ratio, R:B, peak at 656 nm), blue (B, peak at 450 nm), and white (400–700 nm)—were utilized in this study. The combination of red and blue LED lights, along with monochromatic red and blue treatments, significantly enhanced germination traits and early seedling growth compared to white and ambient lighting. The combined spectrum resulted in the highest seedling emergence, the longest shoot and root lengths, and the highest fresh weight. These findings underscore the potential of the LED technology to improve germination efficiency and enhance seedling quality in CEA. Future studies should refine multispectral LED strategies by examining factors such as light intensity and photoperiod, while also elucidating the molecular pathways involved in light-driven germination and early development in lettuce.