Effect of Electrical Conductivity of Nutrient Solution and Light Spectra on the Main Phytochemical Content of Sonchus tenerrimus L. Under Wild and Controlled Environments

<i>Sonchus tenerrimus</i> L. is a wild leafy plant valued for its nutritional and functional properties. This study evaluated how different levels of electrical conductivity (EC) in nutrient solutions and lighting conditions affect the accumulation of bioactive compounds and growth performance in hydroponically cultivated <i>S. tenerrimus</i>. Plants were exposed to four EC treatments (1.2, 1.8, 2.4, and 3.0 dS m^-1), four lighting regimens of natural light, and four artificial-lighting spectra. Total phenolic content (TPC), total flavonoid content (TFC), vitamin C, and antioxidant activity (via DPPH and ABTS assays) were measured. Principal Component Analysis (PCA) was used to assess the relationships among treatments and biochemical responses. The 2.4 dS m^-1 EC level, particularly under natural light, led to the highest TPC, TFC, and antioxidant activity, indicating that moderate salinity enhances phytochemical production. Excessive EC (3.0 dS m^-1) reduced antioxidant levels and plant growth, likely due to stress. Light conditions also influenced results, with natural light generally supporting greater bioactive accumulation and biomass than artificial lighting. These findings suggest that optimizing EC and light exposure can improve both the nutritional value and growth of <i>S. tenerrimus</i>. Future studies should explore the long-term effects, genotype-specific responses, and interaction of these factors with other environmental variables.