Abstract

Biodegradable chitosan nanoparticles have emerged as nanocarriers for the controlled delivery of bioactive molecules in agricultural systems. In this study, S-nitrosoglutathione-loaded chitosan nanoparticles (GSNO-CSNPs) were developed and evaluated as nitric oxide (NO)-releasing nanobiostimulants to mitigate salinity stress in lettuce. A factorial greenhouse experiment combined four salinity levels (0, 0.1, 0.2, and 2 g L-1 NaCl) with four foliar GSNO-CSNPs concentrations (0, 50, 100, and 200 mu M). Physicochemical characterization revealed a stable colloidal system with an average hydrodynamic diameter of 129 nm and a zeta potential of-33.3 mV. GSNO-CSNPs exhibited sustained nitric oxide release for up to 20 h, confirming the suitability of the chitosan matrix as a controlled-delivery. GSNO-CSNPs significantly enhanced plant performance under salinity stress. Under severe salinity (2 g L-1 NaCl), applications of 50-100 mu M increased fresh and dry biomass by up to 19% and 56.7%, respectively, while maintaining net photosynthetic rate, stomatal conductance, and intrinsic water-use efficiency at levels comparable to those of non-stressed plants. The CSNPs treatment also promoted osmotic adjustment through proline accumulation and activated enzymatic antioxidant defenses. Furthermore, GSNO-CSNPs stimulated the accumulation of flavonols and hydroxycinnamic acids, and increased total antioxidant capacity under moderate and severe salinity, indicating enhanced phytochemical quality. The results demonstrate that CSNPs serve as efficient, biodegradable nanocarriers for sustained NO delivery, thereby improving physiological performance, stress tolerance, and bioactive compound accumulation in lettuce. These findings highlight the potential of chitosan-based nitric oxide nanodelivery systems as multifunctional biopolymeric platforms for sustainable crop stress management.