Allelopathic and phytotoxic activity of essential oil of Elaeagnus angustifolia flowers and its major constituents on Amaranthus retroflexus and Lolium perenne

This study investigated the allelopathic and phytotoxic effects of Elaeagnus angustifolia flower essential oil (EO) and its major constituents. Forty-one compounds were identified by GC-MS, accounting for 96.93% of the total oil, with the main compounds being ethyl cinnamate and methyl cinnamate. The allelopathic assay of the EO completely suppressed the seed germination of Lolium perenne and Amaranthus retroflexus at 22.22 mg/mL air treatment. Phytotoxic activities of ethyl cinnamate and methyl cinnamate were much stronger than those of the EO against L. perenne, with IC50 values of 0.386, 0.396, and 7.159 mg/mL, respectively. The strength of the phytotoxic activity of the major constituent ethyl cinnamate, and the mixture of ethyl cinnamate and methyl cinnamate was comparable to that of the commercial herbicide glyphosate in terms of suppressing root elongation in A. retroflexus, with IC50 values of 0.049, 0.076, and 0.017 mg/mL, respectively, indicating a possible synergistic effect of the major compounds.