Phytotoxic Activity of Alkaloids in the Desert Plant Sophora alopecuroides

Abstract

<i>Sophora alopecuroides</i> is known to produce relatively large amounts of alkaloids; however, their ecological consequences remain unclear. In this study, we evaluated the allelopathic potential of the main alkaloids, including aloperine, matrine, oxymatrine, oxysophocarpine, sophocarpine, sophoridine, as well as their mixture both in distilled H₂O and in the soil matrix. Our results revealed that all the alkaloids possessed inhibitory activity on four receiver species, i.e., <i>Amaranthus retroflexus</i>, <i>Medicago sativa</i>, <i>Lolium perenne</i> and <i>Setaria viridis</i>. The strength of the phytotoxicity of the alkaloids was in the following order: sophocarpine > aloperine > mixture > sophoridine > matrine > oxysophocarpine > oxymatrine (in Petri dish assays), and matrine > mixture > sophocarpine > oxymatrine > oxysophocarpine > sophoridine > aloperine (in pot experiments). In addition, the mixture of the alkaloids was found to significantly increase the IAA content, MDA content and POD activity of <i>M. sativa</i> seedlings, whereas CTK content, ABA content, SOD activity and CAT activity of <i>M. sativa</i> seedlings decreased markedly. Our results suggest <i>S. alopecuroides</i> might produce allelopathic alkaloids to improve its competitiveness and thus facilitate the establishment of its dominance; the potential value of these alkaloids as environmentally friendly herbicides is also discussed.