Green-synthesized copper nanoparticles differentially modulate germination and selected stress-response genes in Phelipanche aegyptiaca

Abstract Egyptian broomrape ( Phelipanche aegyptiaca ) is a devastating parasitic weed requiring eco-friendly control strategies. This in vitro study investigated the effects of green-synthesised copper oxide (CuO) nanoparticles, produced using Anethum graveolens extract, on P. aegyptiaca germination and targeted stress-gene expression. Nanoparticles were physicochemically characterised via TEM, DLS, and FTIR. Germination bioassays (1–25 mg L⁻¹ CuO-NPs; 25 mg L⁻¹ bulk CuSO₄) were conducted under four distinct physiological conditions. Under non-inductive conditions, 1 mg L⁻¹ CuO-NPs stimulated germination from ~ 0.7% to ~ 8.1%, indicating a clear hormetic response. Conversely, 10–25 mg L⁻¹ CuO-NPs caused strong germination inhibition and radicle-growth suppression (> 97% reduction), even under optimal strigolactone stimulation. Unlike bulk CuSO₄, CuO-NPs triggered dose-dependent upregulation of antioxidant and phenylpropanoid genes ( SOD , APX , PAL ) and significantly elevated phenolic and flavonoid contents. Furthermore, EDS revealed that CuO-NPs produced more spatially dispersed copper deposition on seed coats compared to localised aggregates formed by bulk copper. These findings demonstrate that green-synthesised CuO-NPs effectively modulate parasitic weed germination and stress-related gene expression in vitro , highlighting their promising potential for targeted seed-bank management pending further comprehensive environmental and host-safety validation.