Amino acid-modified nano-magnetite boosts okra [Abelmoschus esculentus (L.) Moench] yield and iron enrichment for...

Nano-Fe forms could serve as novel fertilizers that can enhance Fe bioavailability. In this study, we synthesized magnetite nanoparticles and complexed nano-Fe₃O₄ with glycine, aspartic acid, and arginine. After synthesis, the amino acid-functionalized Fe-nanoparticles (nFe₃O₄-Gly, nFe₃O₄-Asp, and nFe₃O₄-Arg) were sprayed (75 and 150 mg L^-1) on okra [Abelmoschus esculentus (L.) Moench] plants, and changes in growth, biochemical traits, and their role in agronomic biofortification were investigated during a field experiment using Randomized Complete Block Design (RCBD). It was found that foliar application of these nanoparticles significantly enhanced okra biomass, and the most effective was nFe₃O₄-Gly at 75 mg/L, which enhanced shoot dry weight (+ 70.1%), number of leaves (+ 30.2%), leaf area (+ 48.3%), and number of branches (+ 55.6%) compared to the control. Moreover, foliar treatments positively influenced soluble proteins (up to 1.8 mg/g FW; + 44.4% than control) and free amino acids (up to 1.52 mg/g DW; + 57.8%). Most importantly, Fe concentrations in leaves and okra fruits substantially increased, indicating prominent Fe biofortification. After all, three harvests, okra fruits exhibited up to 0.71 mg/g DW (+ 50.7% than control). Overall, nFe₃O₄-Arg was the most effective for Fe biofortification of okra fruits at a concentration of 75 mg/L. In contrast, the yield per plant was enhanced by both nFe₃O₄-Arg and nFe₃O₄-Asp. In summary, this study demonstrated the potential of amino acid-functionalized Fe nanoparticles in improving growth and Fe bioavailability in okra, offering a promising avenue for addressing Fe deficiency in crops.