Silver Nanoparticles Influence on Growth, Biochemistry, and Yield of Fenugreek (Trigonella foenum-graecum)

The present study investigates the effects of foliar application of Rhizopus-mediated silver nanoparticles (RAgNPs), chemically synthesized AgNPs, and Rhizopus extract on growth, physiological traits, secondary metabolite accumulation, and antioxidant activity in fenugreek ( Trigonella foenum-graecum L.) plants. Treatments at various concentrations (20–100 mg/L) were evaluated, with the 60 mg/L RAgNP application producing the most pronounced responses. RAgNPs significantly increased shoot and root growth, total biomass, yield components, and marked enhancements in photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids, and total pigments). Secondary metabolite analysis revealed substantial increases in total phenolics (121%) and flavonoids (87%) in RAgNP-treated plants, correlating with elevated total antioxidant capacity and ferric reducing antioxidant power (FRAP) activity. Moreover, diosgenin content was enhanced, suggesting activation of the phenylpropanoid pathway and related metabolic routes. The superior performance of RAgNPs over chemically synthesized AgNPs and Rhizopus extract alone is attributed to synergistic effects between the silver nanoparticulate core and fungal bioactive compounds, which act as potent nanoelicitors. These findings highlight biologically synthesized silver nanoparticles as effective tools for improving crop growth, photosynthetic efficiency, antioxidant defense, and producing pharmaceutically valuable metabolites, offering promising applications in sustainable agriculture and medicinal plant biotechnology.