Foliar spray of silicon nanoparticles improved the growth and minimized cadmium (Cd) in wheat under combined Cd and water-limited stress

The effects of foliar supply of silicon nanoparticles (Si-NPs) on growth, physiology, and cadmium (Cd) uptake by wheat ( Triticum aestivum L.) were examined in different soil moisture levels. Seeds were sown in soil containing excess Cd (7.67 mg kg −1 ) and Si-NPs were applied through foliar dressing with various levels (0, 25, 50, 100 mg L −1 ) at different time intervals during growth period. Initially, all pots were irrigated with normal moisture level (70% water-holding capacity) and two moisture levels (35%, 70% WHC) were initiated after 6 weeks of plant growth for remaining growth duration and harvesting was done after 124 days of sowing. The results demonstrated the lowest plant growth, yield, and chlorophyll concentrations while the highest oxidative stress and Cd concentrations in plant tissues in water-stressed control (35% WHC) followed by normal control (75% WHC). Si-NPs enhanced the growth, photosynthesis, leaf defense system, and Si concentrations in tissues while minimized the Cd in wheat parts particularly in grains either soil normal or water-stressed conditions. Of the foliar spray, 100 mg L −1 of Si-NPs showed the best results with respect to growth, Cd and Si uptake by plants, and soil post-harvest bioavailable Cd irrespective of soil water levels. In grain, Cd concentration was below threshold limit (0.2 mg kg −1 ) for cereals in 100-mg kg −1 Si-NPs treatment irrespective of soil water levels. Si-NPs foliar dressing under Cd and water-limited stress might be an effective strategy in increasing growth, yield, and decreasing Cd concentration in wheat grains under experimental conditions. Thus, foliar dressing of Si-NPs minimized the Cd risk in food crops and NPs entry to surroundings, which might be possible after harvesting of crops in soil-applied NPs.