Macronutrient deprivation eustress elicits differential secondary metabolites in red and green‐pigmented butterhead lettuce grown in a closed soilless system

BACKGROUND: ) on the bioactive profile of red and green-pigmented Salanova® butterhead lettuce. RESULTS: Half-strength NS reduced fresh biomass of both cultivars by 14%, whereas quarter-strength NS reduced the fresh biomass of green and red Salanova by 24% and 38%, respectively. However, moderate nutrient stress (half-strength NS) boosted red Salanova total ascorbic acid, chlorogenic, chicoric, caffeoyl-meso-tartaric, total phenolic acids, and anthocyanins concentrations by 266%, 199%, 124%, 251%, 162%, and 380%, respectively compared with the control, full-strength NS. CONCLUSIONS: Nutritional eustress and appropriate cultivar selection are effective means to increase phytochemical content and optimize year-round production of lettuce in closed soilless systems.