Effect of silver nanoparticles synthesized from Stachytarpheta jamaicensis leaf extract on Macrotyloma uniflorum germination

This research focuses on the synthesis of silver nanoparticles (AgNPs) using leaf extract of Stachytarpheta jamaicensis (SJLE) and examines their effectiveness in plant growth stimulation under agricultural conditions. On addition of SJLE to a 1.0 mM AgNO 3 solution, a visible colour change to reddish brown was observed within 45 min, indicating the formation of silver nanoparticles. UV-Vis spectrum depicted a prominent peak at 434 nm, confirming the generation of AgNPs from SJLE (SJ-AgNPs). The one-parameter-at-a-time approach for optimizing synthesis parameters revealed maximum SJ-AgNP formation (SPR at 434 nm) at 5 % (v/v) SJLE, 2.0 mM AgNO3, with a 5 h reaction time. SEM images indicated that the nanoparticles were moderately agglomerated and spherical, with a size range of 10–30 nm. In contrast, EDS confirmed the presence of Ag, C, and O elements, signifying their high purity. The capping of SJLE phytochemicals on the SJ-AgNP surface was confirmed by identification of functional groups such as C – H, C – O – C or C – O, C – N, C= O and O – H. XRD pattern showed peaks at 2Ɵ values corresponding to the (111), (200), (220) and (311) planes confirming the crystalline nature and face centred cubic structure of the AgNPs. Biological evaluation showed that these SJ-AgNPs exhibited a dose-dependent influence on horse gram seed germination and early growth. At low to moderate concentrations (2 – 8 mg/L), the nanoparticles enhanced both germination rate and seedling growth. However, concentrations above 10 mg/L drastically inhibited germination percentage, delayed germination, and reduced seedling biomass and root length, indicating phytotoxicity at elevated levels. • Silver nanoparticles synthesized using Stachytarpheta jamaicensis leaf extract (SJ- AgNPs). • SJ - AgNPs showed SPR at 434 nm with particle size of 10 - 30 nm. • SJ - AgNPs enhanced horse gram seed germination and early seeding growth upto 8 mg/L.