Abstract
The overall goal of the project was to test the hypothesis that Lamium amplexicaule and Lamium purpureum, weedy invasive species to North America, use phytotoxic allelochemicals in interplant competition. The chemical compositions of the essential oils from the aerial parts of L. amplexicaule and L. purpureum have been obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The essential oils and several essential oil components have been screened for phytotoxic activity on lettuce (Lactuca sativa) and perennial ryegrass (Lolium perenne) as well as nematocidal activity against Caenorhabditis elegans, brine shrimp (Artemia salina) lethality, and insecticidal activity against the red imported fire ant (Solenopsis invicta × richteri). L. amplexicaule essential oil was composed largely of α-pinene, β- pinene, 1-octen-3-ol, (E)-caryophyllene, and germacrene D, while L. purpureum oil was dominated by α-pinene, β-pinene, 1-octen-3-ol, β-elemene, and germacrene D. Neither essential oil exhibited notable phytotoxicity or lethality against nema-todes, brine shrimp, or fire ants. It is unlikely, therefore, that the allelopathy observed in these Lamium species is due to volatile phytochemical constituents.
Highlights
Both Lamium amplexicaule L. and Lamium purpureum L. are non-native annual, weedy, invasive species, originally from Eurasia [1]
L. amplexicaule has been shown to reduce the yield of wheat (Triticum aestivum) [4], and L. purpureum has been shown to reduce the growth of soybeans (Glycine max) [5]
We test the hypothesis that volatile phytochemical components from these members of the mint family (Lamiaceae) are responsible for the reported allelopathic effects; we have determined the chemical compositions and biological activities of the essential oils from the aerial parts of L. amplexicaule and L. purpureum growing in fields in and near Huntsville, Alabama
Summary
Both Lamium amplexicaule L. (henbit deadnettle) and Lamium purpureum L. (purple deadnettle) are non-native annual, weedy, invasive species, originally from Eurasia [1]. Invasion of exotic plant species can present a substantial problem to natural ecosystems as well as croplands and pastures [2,3]. Both L. amplexicaule and L. purpureum can aggressively spread through fields, pastures, and gardens. We test the hypothesis that volatile phytochemical components from these members of the mint family (Lamiaceae) are responsible for the reported allelopathic effects; we have determined the chemical compositions and biological activities of the essential oils from the aerial parts of L. amplexicaule and L. purpureum growing in fields in and near Huntsville, Alabama
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