Soil salinity severely limits rice productivity by impairing photosynthesis, disturbing ion homeostasis and accelerating oxidative injury. The study aimed to evaluate the comparative efficacy of biochar (BC), SiO2 nanoparticles (Si-NPs) and their combined composite SiO2 nano-modified biochar (SBC) in enhancing salt tolerance in rice. Material characterization (SEM, TEM, FTIR, XRD) confirmed successful anchoring of SiO2 onto the biochar matrix, forming a highly reactive nano-carbon composite. In this study rice plants under moderate salinity (EC ≈ 7 dS m-1) conditions exhibited pronounced growth inhibition, excessive Na+ accumulation, elevated oxidative damage and impaired photosynthetic performance. In contrast, application of SBC substantially outperformed BC and Si-NPs and markedly alleviated stress symptoms. Relative to the CK-S, SBC reduced H2O2 and MDA by 55.4 % and 38.2 %, respectively, and enhanced SOD, POD and CAT activities by 39.5, 47.3 % and 31.3 %. Photosynthetic performance also improved significantly, with increase of 72.5 % in Pn, 77.2 % in Gs, 178.6 % and in ETR. SBC also improved the osmotic adjustment raising starch and sucrose content by 62.1 % and 70.9 % while reducing excessive proline accumulation by 30.6 %. Ion homeostasis improved through lower Na+ uptake and higher K+ retention resulting in a markedly higher K+/Na+ ratio through application of SBC. Furthermore, SEM imaging and transcript analysis revealed improved stomatal structure and root anatomical resilience while qRT-PCR showed upregulation of key stress-responsive genes associated with antioxidant and ion-transport pathways. These findings demonstrate that SBC provides a synergistic biochar-nanoparticle mechanism that comprehensively enhances rice tolerance to salinity, offering a promising and sustainable amendment for improving productivity in salt-affected agricultural systems.
Sultan et al. (2026) studied this question.