Synergistic herbicidal effects of Nelumbo nucifera Gaertn. leaf extract-silver nanoparticles against Bidens pilosa L.

Abstract

The risks posed by conventional herbicides have driven research toward environmentally friendly alternatives for sustainable agriculture. We synthesized silver nanoparticles (AgNPs) using aqueous extracts from the allelopathic plant Nelumbo nucifera Gaertn. (lotus) leaves, and their herbicidal activities were investigated against farmland weeds. The lotus-assisted AgNPs were characterized using ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The surface plasmon resonance (SPR) band at 459 nm observed from the UV–Vis spectrum confirmed the successful synthesis of AgNPs. The hydrodynamic diameter of the AgNPs, as determined by the dynamic light scattering (DLS) measurement, was 105.1 nm, with a polydispersity index of 0.196. XRD results confirmed the synthesized AgNPs were proven to be crystalline with an average crystallite size of 18.62 nm. TEM analyses revealed that the AgNPs exhibited a spherical morphology with an average particle size of 12.87 nm. The herbicidal activities against Bidens pilosa L. of these lotus-mediated AgNPs were tested using both the Petri dish method and the soil irrigation method. The plant-derived AgNPs demonstrated a greater inhibitory effect on the seed germination and seedling growth of B. pilosa than the lotus extract. The results from herbicidal tests demonstrated that the synergetic herbicidal activity was realized after combining lotus extract with AgNPs. This study provided a new alternative to synthesize AgNPs by allelopathic plants, which could be used as botanical nanoherbicides for weed management in sustainable agriculture.

Graphical abstract