Precision nanobubble irrigation tailors plant physiology to drive sustainable lettuce growth with water savings

Under accelerating climate-driven water scarcity, improving irrigation efficiency for high-value leafy crops has become an urgent challenge for global food security. Nanobubbles (NBs), gas-filled cavities < 500 nm in diameter, have emerged as a promising irrigation technology capable of enhancing root-zone processes and early plant development with minimal additional water inputs. However, their effects in soil-based systems remain poorly resolved, particularly for leafy vegetables grown in water-stressed regions. Here, we systematically evaluate the influence of four gas types (O₂, CO₂, N₂, and air), delivered as NBs at three dilution levels (100 %, 50 %, and 10 %; corresponding to >10⁸ particles mL⁻¹ at 100 %), on early-stage growth and water productivity (WP) in lettuce ( Lactuca sativa, var. 'Little Gem') grown in a peat moss, coconut coir, and vermiculite mixture. Our results reveal that moderately diluted O₂ NBs (10 %–50 %) accelerate germination, boost biomass accumulation, and improve water savings by up to ∼23 %. In contrast, high concentrations (100 %) of O₂ NBs reduced overall performance and induced elongated but narrow leaf morphology, consistent with stress-related growth allocation. The use of CO₂ NBs, particularly at higher concentrations, stimulates root expansion and leaf area development, while moderate N₂ NBs concentration enhanced ammonium uptake and root elongation. Air NBs produce modest and variable effects, serving as a baseline but never outperforming pure gas NBs. Together, these results demonstrate that gas-specific NBs treatments can be strategically tuned to regulate distinct physiological pathways during early plant development, supporting the potential of NBs-based irrigation as a tool for water-efficient, climate-resilient leafy crop production.