Biochar and nano-silicon partnership alleviates vanadium toxicity in rice through improving antioxidant defense, nitrogen assimilation and iron plaque formation

Introduction Biochar (BC) and nano-particles have emerged as promising strategies to mitigate heavy metal toxicity and remediate polluted soils. Vanadium (V) is a toxic metal posing hazardous impacts to plants and humans. The role of BC and nano-particles, particularly their combination to alleviate V toxicity, is poorly understood. Thus, this study explored the role of BC and silicon nano-particles (Si-NPs) partnership in mitigating the V toxicity in rice. Methods The study has five treatments: control, V stress (30 mg kg -1 soil), V stress (30 mg kg -1 soil) + biochar (3%), V stress (30 mg kg -1 soil) + Si-NPs (150 mg kg -1 soil), and V stress (30 mg kg -1 soil) + biochar (3%) + SiO-NPs (150 mg kg -1 soil). Results The study results revealed that V toxicity decreased rice growth by declining root growth, chlorophyll pigments (78.72-111.50%), nitrogen assimilation, and increasing oxidative stress, membrane damage, and V accumulation in rice plants. Biochar + Si-NPs enhanced rice biomass (20.33%) and grain yield (67.64%) by increasing antioxidant activities (54.12-99.38%), nutrient uptake (58.80-81%), osmolytes synthesis, and decreasing V accretion in rice roots (64.05%) and shoots (91.65%). This increase in rice growth was also linked with an increase in activity of nitrogen assimilation enzymes (nitrate reductase: NR, 65%, glutamine synthetase: GS, 71.82%, glutamate synthase: GOGAT, 106% and glutamate dehydrogenase: GH, 25%) and iron plaque formation. Conclusion These findings suggest that the partnership between BC and Si-NPs enhanced root growth, chlorophyll synthesis, antioxidant activity, nitrogen assimilation, and iron plaque formation, while decreasing oxidative damage and V accumulation, thereby increasing plant growth. Thus, a combination of BC and Si-NPs can be an important strategy to mitigate the V toxicity and enhance rice production in V-polluted soils.