Enhancing water deficit tolerance in canola (Brassica napus L.) through the synergistic application of nano-silicon and sulfur

Water deficit stress is a critical constraint on global crop productivity, particularly in arid and semi-arid regions, where it severely compromises plant growth, yield, and nutritional quality. Sustainable strategies to enhance plant resilience under such conditions are urgently needed. Nano-silicon (Si-NPs) and sulfur (S) have emerged as promising amendments for mitigating abiotic stress, but their synergistic potential in alleviating water deficit stress in oilseed crops like canola (Brassica napus L.) remains underexplored. This study investigated the combined effects of Si-NPs (0, 100, 200, and 300 mg kg⁻¹) and sulfur (0, 75, and 150 mg S kg⁻¹) on the morphological, physiological, and nutritional responses of canola under three water deficit levels (0.8, 0.6, and 0.4 field capacity). Results demonstrated that water deficit stress significantly reduced photosynthetic efficiency, biomass accumulation, and yield components. However, Si-NPs and S application counteracted these adverse effects. Specifically, 100 mg Si-NPs kg⁻¹ increased shoot and root weights by 19.3% and 22.9%, respectively, compared to the control. The most effective treatment-200 mg Si-NPs kg⁻¹ combined with 75 mg S kg⁻¹-enhanced chlorophyll (1.76 mg g⁻¹ FW), carotenoids (0.51 mg g⁻¹ FW), phosphorus uptake (0.85%), and silicon accumulation in shoots (4.3%), while reducing lipid peroxidation (malondialdehyde: 23.53 µg g⁻¹ FW). These findings highlight the synergistic role of Si-NPs and S in improving drought resilience by enhancing photosynthetic capacity, nutrient homeostasis, and oxidative stress mitigation. This study provides actionable insights for integrating nano-enabled and sustainable nutrient management practices to bolster crop productivity in water-scarce agroecosystems. Future research should validate these results under field conditions and elucidate the molecular mechanisms driving these stress-adaptive responses.