Echinacea purpurea morphological and biochemical response to combined LED light and sucrose level in in vitro culture

Abstract Echinacea purpurea , a widely cultivated medicinal and ornamental plant, produces diverse biochemical compounds with immunostimulatory, anti-inflammatory, and antioxidant properties. Optimizing in vitro propagation conditions, particularly LED light and sucrose level, is essential to enhance plantlet quality and biochemical performance for large-scale production. In this study, plantlets were exposed to four LED spectrum, W/R (85% white + 15% red), B/WR (20% white + 60% blue + 20% red), BR/W (20% white + 40% blue + 40% red), and R/WB (20% white + 20% blue + 60% red). The interaction between LED light and sucrose level significantly affected growth parameters, photosynthetic pigments, hydrogen peroxide (H₂O₂) content, catalase (CAT) activity, free amino acids (FAA), soluble protein, total soluble sugars (TSS), reducing sugars (RS), as well as total polyphenolic acids content (TPC) and total flavonoid content (TFC) of the plant. BR/W and R/WB LEDs combined with high sucrose levels (30 g·L⁻¹) promoted shoot elongation and induced oxidative stress, as reflected by elevated H₂O₂ and CAT activity. Conversely, W/R and B/WR light with moderate sucrose concentrations (10 and 20 g·L⁻¹) enhanced chlorophyll, TSS, and FAA levels, supporting balanced growth with lower stress indicators. Pigment production was more strongly influenced by light than by sucrose, while RS and antioxidant responses increased under stress-inducing conditions. TPC peaked under B/WR LEDs with 10 g·L⁻¹ sucrose, whereas TFC accumulation was highest under moderate oxidative stress. Statistical interactions between LED light and sucrose were significant for multiple parameters, highlighting the synergistic role of these factors in shaping in vitro growth, metabolic activity, and biochemical composition of the plant. These results highlight the importance of fine-tuning light quality and sucrose levels to optimize growth and biochemical compounds production in E. purpurea micropropagation systems.