Silicon dioxide nanoparticles enhance phytoremediation potential while contributing to the safer production of Chenopodium quinoa Willd. in Pb-contaminated soils

Nanotechnology has emerged as an attractive approach for remediating soils contaminated with heavy metals. However, the effect of silicon nanoparticles (Si NPs) on the tolerance and accumulation of Pb in quinoa ( Chenopodium quinoa Willd.) remains largely unexplored. Therefore, the current study assessed the effectiveness of silicon dioxide nanoparticles (nSiO 2 ) on the phytoremediation capacity and yield of quinoa. Adding 400 and 800 mg kg −1 of Pb to the soil adversely affected the growth, seed yield, and tolerance index. The application of nSiO 2 significantly increased the Si content in the shoots and roots, chlorophyll a and b levels, relative water content, growth parameters, and seed yield. It also enhanced the concentrations of P, K, and Ca 2+ in the shoots and seeds at all Pb levels. Moreover, soil amendment with 1000 mg kg −1 of nSiO 2 decreased hydrogen peroxide (33.65 % and 35.73 %) and malondialdehyde (34.97 % and 40.23 %) contents in the leaves by improving the activities of catalase (30.25 % and 25.56 %) and peroxidase (38.19 % and 29.6 %) enzymes. This treatment also upregulated the expression of the P5CS gene (33.33 % and 51.75 %) and increased proline accumulation (91.42 % and 65.89 %) at 400 and 800 mg kg −1 Pb. Applying 1000 mg kg −1 of nSiO 2 reduced root-to-shoot (15.68 %) and shoot-to-seed (7.14 %) translocation of Pb, resulting in an increase in seed yield (70.4 %) and decreasing Pb concentrations in shoots (31.67 %), and seeds (45.28 %) at 800 mg kg −1 Pb. Interestingly, soil amendment with nSiO 2 , particularly at a concentration of 500 mg kg −1 , increased total Pb uptake per plant by 18.5 % and 10.3 % at 400 and 800 mg kg −1 Pb respectively, thus enhancing Pb phytostabilization capacity. These findings provide novel evidence that Si NPs can enhance the phytoremediation potential of quinoa plants by maintaining biomass while reducing Pb toxicity through the “growth dilution effect,” leading to increased seed yield and improved food security.