Phytotoxic characterization of Chrysopogon zizanioides root extracts: inhibitory effects on Eleusine indica and Praxelis clematidea

Abstract

ABSTRACT The reliance on synthetic herbicides has accelerated herbicide resistance, necessitating the development of sustainable, plant-based management strategies. This study evaluated the phytotoxic potential of the root methanolic extract of Chrysopogon zizanioides (vetiver grass) against two noxious weeds, Praxelis clematidea and Eleusine indica. Greenhouse experiments assessed pre- and post-emergence effects at concentrations of 0, 0.1, 10, 50, and 100 mg·mL-1, focusing on growth, photosynthetic, and stress biomarkers. The extract displayed significant, species-specific phytotoxicity. In early post-emergence trials, E. indica exhibited higher sensitivity (63.3% inhibition) compared to P. clematidea (36.7%). Conversely, post-emergence applications caused severe growth suppression in P. clematidea, reducing shoot and root biomass by 91 and 95%, respectively. While E. indica experienced moderate biomass loss (59–69%), it suffered pronounced physiological disruption, evidenced by significant declines in soil-plant analysis development values (SPAD) (34%) and chlorophyll a content (35%). Biochemical analyses indicated that phytotoxicity was mediated by an oxidative burst, as evidenced by elevated proline, malondialdehyde, and superoxide dismutase activity. The results also indicated that the extract was effective in early post-emergence treatment against monocot weed, while inflicting damage on dicot weed in post-emergence treatment. These findings demonstrated that C. zizanioides extracts effectively inhibit weed growth by disrupting photosynthetic machinery and inducing oxidative damage, highlighting their potential as bio-herbicides.