Fresh/brackish watering at growth period provided a trade-off between lettuce growth and resistance to NaCl-induced damage

Abstract

Supply with fresh and brackish water at different growth periods of crops is an effective strategy to alleviate freshwater shortage and ensure food security. However, the potential mechanisms are not well understood. To bridge this gap, comparative physiological, transcriptomic and metabolomic profiling was used to analyze lettuce grown under four treatments [exposure to non-saline (NS) nutrient solution during full growth period, NS-NS; exposure to saline (S, 30 mM NaCl added to NS) nutrient solution during early, later or full growth period, S-NS, NS-S and S-S]. The results showed that after brackish water exposure, lettuce showed growth inhibition and reactive oxygen species accumulation, and the dry weight was significantly reduced under S-NS and S-S but not NS-S. NS-S saved fresh water consumption compared to NS-NS and significantly improved the brackish water use efficiency compared to S-NS and S-S. In addition, brackish water exposure regulated the antioxidant system, and activated the metabolic process related to sugar synthesis. Together, this study provides evidence of the protective roles of exposure to brackish water for only later of the lettuce growth period, and it's a valuable water supply reference for cultivating crops with brackish water in water-scarce regions.