Integrated Multivariate and Random Forest Analysis of LED Light Effects on Quality-Related Traits of Endive Microgreens

The study evaluated the effects of different LED light spectra on the morphological characteristics, photosynthetic pigments, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (DPPH) of endive microgreens, and identified biochemical parameters associated with light responses using correlation analysis, principal component analysis (PCA), and the Random Forest model. Microgreens were grown under different LED light spectra (blue, red, blue–red, cool white and darkness) in controlled growth chamber conditions under a long-day photoperiod (16 h light/8 h dark). Analysis of variance (ANOVA) demonstrated that LED light quality significantly affected all morphological and biochemical traits. The highest fresh weight (0.246 g) and total chlorophyll content (8.475 mg/g FW) were obtained under the b-RED treatment, whereas the highest TPC was recorded under blue light (B; 4.497 mg GAE/g FW). The greatest antioxidant activity was observed under the combined red-blue spectrum (RB; 19.573 mg TXE/g FW), while red light and darkness resulted in the lowest values for most analyzed parameters. Correlation analysis revealed strong positive associations among photosynthetic pigments, phenolic compounds, and antioxidant potential, with the strongest correlation observed between TPC and DPPH (r = 0.858, p < 0.01). PCA explained 88.8% of the total variance and clearly separated treatments containing a blue light component from those exposed to red light or darkness. Random Forest analysis identified TPC as the most important discriminating variable among LED treatments, followed by stem length, DPPH, and Total Chl. Overall, blue-containing LED spectra, particularly in combination with red light, improved morphological (b-RED) and biochemical characteristics of endive microgreens (RB). The b-RED treatment was the most effective in improving morphological characteristics and chlorophyll accumulation, while the red:blue treatment produced the highest antioxidant activity.