How the nutrient flow environment promotes lettuce growth in hydroponics

Hydroponics is a plant growth system that uses liquid nutrient medium, but the effects of nutrient solution flow on root development are unexplored. Here, the comprehensive effects of nutrient flow on root morphology, antioxidant properties, and multi-omics characteristics of hydroponic lettuce were analyzed via root morphology, cell wall composition, oxidative stress indicators, and nutrient uptake at different nutrient flow and growth stages measurement. Under flow conditions, root length, surface area, and volume increased significantly, indicating that flow promoted root expansion and improved nutrient uptake. Cell wall components also increased, suggesting that flow may support root growth by strengthening the cell wall structure. Although oxidative damage indicators increased, the roots also exhibited high antioxidant enzyme activity, enhancing their response to oxidative stress induced by the flowing environment. Metabolomic analysis showed that flow activated cell division- and signal transduction-related pathways. Transcriptomics and proteomics showed the upregulation or downregulation of multiple genes and proteins related to root development and stress resistance, with significant enrichment in the lignin synthesis pathway. Nutrient solution flow, thus, promotes lettuce root growth and stress resistance through multilevel regulation, providing a theoretical basis for enhancing hydroponic crop growth environments, increasing yields, and improving vegetable crop quality.