Seed priming with Fe3O4-SiO2 nanocomposites simultaneously mitigate Cd and Cr stress in spinach (Spinacia oleracea L.): A way forward for sustainable environmental management
Muhammad Irshad, Jamilur R. Ansari, Ali Noman, Wasim Javed, Jong Cheol Lee, Muhammad Aqeel, Muhammad Waseem, Sang Soo Lee
Abstract
Seed priming with a composite of iron oxide (Fe 3 O 4 ) and silicon dioxide (SiO 2 ) nanoparticles (NPs) is an innovative technique to mitigate cadmium (Cd) and chromium (Cr) uptake in plants from rooting media. The current study explored the impact of seed priming with varying levels of Fe 3 O 4 NPs, SiO 2 NPs, and Fe 3 O 4 -SiO 2 nanocomposites on Cd and Cr absorption and phytotoxicity, metal-induced oxidative stress mitigation, growth and biomass yield of spinach ( Spinacia oleracea L.). The results showed that seed priming with the optimum level of 100 mg L −1 of Fe 3 O 4 -SiO 2 nanocomposites significantly ( p ≤ 0.05 ) increased root dry weight (144 %), shoot dry weight (243 %) and leaf area (34.4 %) compared to the control, primarily by safeguarding plant's photosynthetic machinery, oxidative stress and phytotoxicity of metals. Plants treated with this highest level of Fe 3 O 4 -SiO 2 nanocomposites exhibited a substantial increase in photosynthetic and gas exchange indices of spinach plants and enhanced activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) antioxidant enzymes by 45 %, 48 %, and 60 %, respectively. Correspondingly, the relative gene expression levels of SOD, CAT, and APX also rose by 109 %, 181 %, and 137 %, respectively, compared to non-primed plants. This nanocomposite application also boosted the levels of phenolics (28 %), ascorbic acid (68 %), total sugars (129 %), flavonoids (39 %), and anthocyanin (29 %) in spinach leaves, while significantly reducing Cd (34.7 %, 53.4 %) and Cr (20.2 %, 28.8 %) contents in plant roots and shoots, respectively. These findings suggest that seed priming with Fe 3 O 4 -SiO 2 nanocomposites effectively mitigated the toxic effects of Cd and Cr, enhancing the growth and biomass yield of spinach in Cd and Cr co-contaminated environments, offering a promising sustainable approach for producing metal-free crops. • Seed priming with Fe 3 O 4 -SiO 2 nanocomposite suppressed oxidative stress in spinach plants. • This nanocomposite enhanced the relative gene expression levels of antioxidant enzymes. • It boosted plant biomass by protecting photosynthetic machinery and metal phytotoxicity. • This Fe 3 O 4 -SiO 2 nanocomposite significantly reduced Cd and Cr uptake by plants.