Phytochemical mediated green synthesis of molybdenum-based nanoparticles for enhancing seedling vigour and early establishment of greengram (Vigna radiata L.).

Abstract

Background: Sustainable micronutrient management is vital for early crop establishment in legumes, as conventional molybdenum fertilizers often exhibit low bioavailability during early growth stages. In legumes, molybdenum plays an important role in nitrogen fixation and root nodule functioning through nitrogenase and nitrate reductase enzymes. Therefore, phytochemical-mediated molybdenum-based nanoparticles were synthesized and evaluated as a seed treatment for improving seedling vigour and early establishment of greengram (Vigna radiata L.) during 2024-2025 at the Department of Agronomy, University of Agricultural Sciences, GKVK, Bengaluru, India.

Results: The research examined how the phytochemical composition involved in the green synthesis of molybdenum-based nanoparticles influences seedling vigour responses in greengram (Vigna radiata L.). Molybdenum-based nanoparticles were synthesized using aqueous extracts of six plant species (Azadirachta indica, Centella asiatica, Citrus limetta, Psidium guajava, Simarouba glauca and Vitex negundo) with ammonium heptamolybdate as the precursor. Differences in phenolic and flavonoid content among extracts influenced nanoparticle formation, which was characterized using UV-Visible spectroscopy, particle size analysis, SEM, EDX and FTIR. A marked reduction in phenolic and flavonoid contents after synthesis confirmed the direct involvement of phytochemicals in nanoparticle reduction and stabilization. Among the tested extracts, Vitex negundo produced comparatively smaller and more uniform nanoparticles, with a Z-average particle size of 17.13 nm and a dominant size distribution peak accounting for 79.5% intensity, and was therefore selected for biological evaluation. Seed priming with green synthesized molybdenum-based nanoparticles resulted in clear improvements in seedling growth parameters without affecting germination percentage. The highest shoot length (18.84 cm), root length (16.49 cm) and seedling vigour index (3533) were recorded when seeds were primed at 200 ppm for 30 min, representing a substantial increase over hydro-primed control seedlings. Lower concentrations produced moderate improvements, whereas concentrations above 200 ppm caused a decline in shoot and root growth, indicating a narrow optimal dose range and phytotoxicity at higher concentrations.

Conclusions: These findings demonstrate that plant-based phytochemicals strongly influence the green synthesis of molybdenum-based nanoparticles and its performance and that optimized molybdenum-based nanoparticles priming can significantly enhance early seedling vigour, offering a sustainable strategy for improving early crop establishment in legume-based agroecosystems.