Synergistic Effects of Arachidonic Acid Elicitation and Pulsed LED Lighting on Growth and Steviol Glycoside Production in Stevia rebaudiana under Vertical Hydroponics

Background Vertical farming is emerging as a sustainable solution to meet the rising global demand for high-quality medicinal crops by enabling resource-efficient, year-round production independent of climate. Stevia rebaudiana, valued worldwide for its zero-calorie steviol glycosides, requires robust seedling establishment and optimized secondary metabolites in vertical hydroponic systems. This study investigated the interactive effects of exogenous arachidonic acid (ARA) and three lighting regimens (ambient, continuous LED, and pulsed LED) on the growth, physiology, and phytochemical profile of Stevia rebaudiana in a vertical hydroponic system. A two-factor experiment was conducted using foliar ARA applications (0, 25, and 40 µM L⁻¹) and three light regimes on tissue-cultured seedlings. Results Synergistic interactions were observed between 40 µM L⁻¹ ARA and pulsed LED light (PSL), significantly enhancing plant height (+ 19%), stem diameter (+ 43%), leaf area (+ 29%), and aerial fresh weight (+ 28%) compared to the control. This combination also improved chlorophyll a (+ 15%), net photosynthetic rate (+ 33%), proline content (+ 32%), and antioxidant enzyme activities (SOD + 54.9%, POD + 50%). Stevioside content reached its highest level (5.80% of leaf dry matter, + 81%) under 40 µM L⁻¹ ARA + PSL, while rebaudioside A was maximized with 25 µM L⁻¹ ARA under ambient light. Additionally, pulsed LED lighting significantly increased total flavonoid content (+ 38%) and overall antioxidant capacity (+ 30%). Conclusion These findings demonstrate that integrating ARA elicitation with pulsed LED illumination is an effective and sustainable approach to simultaneously optimizing biomass yield and the nutritional-pharmaceutical quality of Stevia rebaudiana in vertical farming systems. The synergy between ARA and pulsed light offers a promising strategy for enhancing both growth and bioactive compound production under controlled environments.