Artemisia argyi essential oil exerts herbicidal activity by inhibiting photosynthesis and causing oxidative damage

Aromatic plant extracts, especially essential oils (EOs), can be used as alternatives to synthetic herbicides due to their effectiveness and easy degradation in environment. Rich in essential oils, Artemisia argyi is a plant that is known for both its medicinal and allelopathic properties. In this study, the chemical composition of A. argyi essential oil (AEO) was examined. Gas chromatographymass spectrometry (GCMS) revealed that relatively high amounts of monoterpenes, including eucalyptol (26.08%), thujone (10.84%), β-caryophyllene (7.46%), borneol (5.09%), and camphor (4.03%), were detected in AEO. Furthermore, AEO was found to inhibit seed germination of Echinochloa crus-galli, Setaria viridis, Portulaca oleracea, and Amaranthus retroflexus as well as kill seedlings of these plants in petri dish experiments. The IC50 values of E. crus-galli, S. viridis, P. oleracea and A. retroflexus were 5.51, 1.02, 25.41, and 0.61 μL/dish, respectively. We demonstrated that A. argyi essential oil aqueous emulsion (AEOAE) exhibited broad-spectrum herbicidal activity and significant short-term contact killing effects on weed plants in both pot and field experiments. S. viridis was taken as a model weed and various physiological indicators were assessed. The results showed that AEOAE induced excessive ROS production in the tested samples, producing an imbalance of the antioxidant system and damage to the integrity of cell membranes, which manifests as increased MDA content and electrolyte leakage. Molecular docking experiments indicated all of above components as potential binding sites with 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzymes, which regulate the biosynthesis of plant tocopherols and plastid quinones to ultimately generate carotenoids. Additionally, AEOAE treatment led to the decrease of HPPD, carotenoid and chlorophyll content in target weeds, revealing that AEOAE may act as an HPPD inhibitor to impede photosynthesis in weed species. Hence, AEO has the potential to be utilized as a source for bio-herbicides that could be adapted for industrial-level production in the future, but its long-term effects should be studied further.