Optimizing Valerianella locusta L. Growth and Metabolism by Combining Red and Blue LED Light: Insights into Plant Physiology, Biochemistry, and Nutraceutical Value

Environmental and health concerns have increased the demand for ready-to-eat vegetables rich in bioactive compounds. This study explores the impact of red and blue (R:B) LED light on the metabolic responses of lamb’s lettuce (Valerianella locusta L.), focusing on sugars, organic acids, total phenolics, antioxidant activity, and enzyme inhibition. Post-harvest analyses were also conducted to assess shelf-life and microbiological characteristics of the product. The R:B LED treatment significantly enhanced plant growth, with a 133% and 68% increase in shoot fresh and dry weights, respectively, and a 21% increase in leaf area compared to controls (white LED light). Biochemical profiling revealed substantial increases in fructose (255%), sucrose (169%), citric acid (350%), and malic acid (868%) under R:B LED light. Additionally, phenolic content increased by 30%, alongside a notable modulation of 258 secondary metabolites, including flavonoid glycosides, alkaloids, and terpenoids. These biochemical changes contributed to a marked improvement in antioxidant capacity (12–45% across multiple assays) and a 300% increase in α-glucosidase inhibition, suggesting potential antidiabetic properties. Furthermore, post-harvest analysis revealed comparable shelf-life and microbiological safety between R:B and white LED-grown samples. The research highlights the potential of LED light to enhance plant biochemical responses and improve crop quality without affecting post-harvest quality, paving the way for sustainable agricultural innovations.