Pristine and zinc-incorporated graphitic carbon nitride: An eco-compatible seed priming agent to mitigate salinity stress in rice

Salinity stress exacerbated by climate change has consequently threatening global rice production. Despite the existing numerous strategies to enhance rice salinity tolerance, the utilization of sustainable nanomaterials as seed priming agents remains insufficiently explored. Therefore, this research assesses the effectiveness of zinc-incorporated and pristine graphitic carbon nitride (g-C 3 N 4 and Zn/g-C 3 N 4 ) nanosheets, synthesized via single-step thermal polycondensation of urea, in augmenting salinity tolerance in rice. The synthesized g-C 3 N 4 have a two-dimensional, lamellar few-layer sheet morphology, with an approximate 3-10 nm thickness, and the matrix is uniformly distributed with Zn (0.7 at%), without any secondary ZnO phases. The folded ultrathin structure of the nanosheets facilitates enhanced seed surface interaction. The implementation of g-C 3 N 4 and Zn/g-C 3 N 4 as priming agents mitigated the reduction in germination percentage and biomass accumulation triggered by NaCl stress. Zn/g-C 3 N 4 priming outperformed g-C 3 N 4 , in effectively mitigating salinity-induced membrane damage through the reduction of lipid peroxidation and ROS accumulation, ascribed to enhanced antioxidant defence mechanism. Elevated Zn levels enhanced membrane stabilization, thus facilitating Na + /K + homeostasis. Nano-priming activated redox-regulatory pathways via Ca 2+ and ABA-mediated upregulation of genes such as OsCu/ZnSOD , OsPOX1 , and OsAPX , consequently improving antioxidant biosynthesis. The differential regulation of OsSOS1 and OsNHX1 facilitated the effective management of Na + transport and vacuolar sequestration, thus preventing ionic toxicity. Therefore, this study presents a novel, scalable and environmentally sustainable method, wherein the incorporation of Zn into a redox-active π-conjugated g-C 3 N 4 framework provides a multifunctional priming platform that enhances antioxidant activities and maintains ionic equilibrium to improve salinity resilience and promote climate-resilient rice cultivation. • Priming established a nano-coating over rice seeds, shielding from salinity stress. • Zn/g-C 3 N 4 nano priming improved rice seed germination and biomass under salinity. • Nano priming mitigated salinity induced oxidative damage and Na + /K + imbalance. • Priming induced Zn accumulation aided in enhanced antioxidant defence mechanism. • Nano priming enhanced rice saline tolerance through differential gene regulation.