Graphitic Carbon Nitride as a Nanostimulant in Basil Microgreens: Insights into Growth, Flavonoid Content, and Water Stress Response

Graphitic carbon nitride (g-C₃N₄) exhibits strong adsorption and photocatalytic activity through reactive oxygen species generation, which also mediate plant stress responses. This study evaluated the effects of g-C₃N₄ on growth and secondary metabolites in basil (Ocimum basilicum L.) microgreens under water deficit. The nanomaterial was synthesized by calcination and characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and dynamic light scattering-electrophoretic light scattering (DLS-ELS). Plants were grown under two hydration regimes (50 and 100% water replacement) and five g-C₃N₄ concentrations (0-250 mg L⁻¹). Foliar applications were performed at 7 and 14 days after sowing, and plants were harvested at day 21. Under 50% water replacement, g-C₃N₄ enhanced growth, increasing leaf area by 34% at 100 mg L⁻¹, stem length by 23 and 19% at 50 and 100 mg L⁻¹, respectively, and root length by 17% at 250 mg L⁻¹ compared to the untreated control. Terpenoid profiles remained unchanged, while flavonoid content increased by 49.98% and 42.87% at 100 and 200 mg L⁻¹, respectively, under water stress. Overall, g-C₃N₄ acted as a modulator of physiological responses, enhancing stress tolerance in basil microgreens.