Enhancing salinity stress tolerance in lemongrass (Cymbopogon citratus L.) using foliar-applied silicon nanoparticles

Salinity stress is a major abiotic constraint limiting the growth, productivity, and essential oil quality of medicinal and aromatic plants, including lemongrass (Cymbopogon citratus). Therefore, this study was conducted during the 2022 and 2023 seasons to evaluate the effects of different salinity levels and silicon nanoparticle (SiNPs) applications on vegetative growth, rhizome characteristics, nutrient status, and essential oil yield and composition of lemongrass plants. The experiment aimed to (i) assess the impact of irrigation water salinity (0.7, 2, 4, and 6 dS m^-1) on plant performance, (ii) investigate the role of SiNPs applied as a foliar (400, 800, and 1200 mg L^-1) treatments in alleviating salinity stress, and (iii) determine the interaction effects between salinity levels and SiNPs on growth and oil productivity. The results revealed that low salinity levels (0.7 and 2 dS m^-1) significantly enhanced vegetative growth parameters, including plant height, number of tillers and leaves, biomass accumulation, and leaf area, as well as rhizome traits and essential oil yield, compared with higher salinity levels. In contrast, increasing salinity (4 and 6 dS m^-1) markedly reduced growth, nutrient uptake (N, P, and K), and oil productivity, while increasing proline accumulation. The application of SiNPs, particularly at 1200 mg L^-1 (foliar), significantly mitigated the adverse effects of salinity by improving growth traits, enhancing photosynthetic efficiency, and promoting nutrient uptake. Moreover, SiNPs positively influenced essential oil yield and modified its chemical composition, increasing key constituents such as citral and related compounds under stress conditions. In conclusion, silicon nanoparticles effectively enhanced lemongrass tolerance to salinity stress and improved both yield and quality across both growing seasons. The combined application of appropriate salinity management and SiNPs represents a promising strategy for sustainable cultivation of lemongrass under saline environments.