Elucidation of Diatom Impregnated with Iron Nanoparticles as a Bio-Stimulator in Early Growth and Development of Rice

ABSTRACT: Merging nanotechnology with biology, diatoms reveal an extraordinary capacity to fabricate iron nanoparticles (INPs) while simultaneously acting as nutrient carriers for crops. The marine diatom Halamphora subturgida was employed for the first time to synthesize INPs and evaluate their application as a nanophycofertilizer (NPF) for rice (Oryza sativa L.). The diatom facilitated both intra- and extracellular formation of spindle-shaped nanoparticles (70–100 nm) as confirmed by UV–Vis, DLS, TEM, SEM-EDAX, FTIR, and fluorescence analyses. Biochemical profiling revealed dynamic metabolic shifts during nanoparticle synthesis, with transient increases in pigments, proteins, and lipids followed by their decline, while iron and carbon content rose steadily. Antioxidant enzyme assays indicated early oxidative stress followed by metabolic adaptation, underscoring the diatom’s resilience as a biofactory. When applied to rice seedlings, the INP-loaded diatoms significantly outperformed diatoms or nanoparticles alone, increasing shoot length by approximately 45%, root length by 50%, fresh biomass by 18%, chlorophyll content by 42%, iron accumulation by nearly twofold, and silica uptake by about 43% compared with the untreated control. These synergistic effects highlight the dual role of diatoms as both stabilizers and nutrient carriers, delivering iron in a highly bioavailable form while simultaneously contributing silica for structural strength. The findings position diatom-mediated nanofertilizers as sustainable alternatives to chemical fertilizers, offering a multifaceted strategy to boost crop vigor, nutrient density, and early-stage resilience in rice.