Evaluation of allelopathic competency of Lamium amplexicaule and identification of its allelopathic active substance

Arihiro Iwasaki, Kiyotake Suenaga,Hisashi Kato- Noguchi,Chisato Sakamoto, Masahiko Suzuki

doi:10.9755/ejfa.2019.v31.i2.1907

Arihiro Iwasaki, Kiyotake Suenaga, Hisashi Kato- Noguchi + Show 1 more

Open Access

https://doi.org/10.9755/ejfa.2019.v31.i2.1907

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Abstract

The weedy annual grass Lamium amplexicaule (L.) originated from the Mediterranean region, spreads quickly, and becomes naturalized in areas it invades. It was assumed that volatile phytotoxic substances are one of the invasive characteristics of L. amplexicaule. However, no volatile compound has been found. Therefore, we re-evaluated the allelopathic potential of L. amplexicaule and investigated the phytotoxic substances with allelopathic activity. An extract of L. amplexicaule inhibited the root and shoot growth of Lepidium sativum, Lactuca sativa, Arctium lappa, Lolium multiflorum Lam., Echinochloa crus-galli, and Vulpia myuros, which indicates that the extract has an allelopathic effect. The extract was purified using bioassay-guided chromatographic separations, and a phytotoxic substance with allelopathic activity was isolated and characterized as methyl caffeate. The compound significantly inhibited the root and shoot growth of L. sativum and L. multiflorum. The present results suggest that methyl caffeate may contribute to the allelopathic effect of the L. amplexicaule extracts and consequently, may be partly responsible for the invasive characteristics of the species.

Highlights

Lamium amplexicaule (L.) is a weedy annual plant species of the Lamiaceae family that originated from the Mediterranean region and spread in Europe, Asia, and northern Africa
The extracts of L. amplexicaule had an allelopathic effect on both the dicotyledonous and monocotyledonous plants. These results suggest that L. amplexicaule may contain phytotoxic substances with allelopathic activity
The IC50 values of the extracts on the test plants were in the range of 38.5–137 mg fresh weight equivalent extract mL−1 for L. sativum, L. sativa, and A. lappa and in the range of 126–937 mg fresh weight equivalent extract mL−1 for L. multiflorum, E. crus-galli, and V. myuros

Summary

Introduction

Lamium amplexicaule (L.) is a weedy annual plant species of the Lamiaceae family that originated from the Mediterranean region and spread in Europe, Asia, and northern Africa. The species has adapted to quickly grow in crop fields, gardens, and pastures (USDA-NRCS, 2015; Stojanova et al, 2016). It competes with crops and other plant species and is categorized as an invasive alien weed in the USA and Canada (CABA, 2018). The interactions of the invasive plants with natural enemies are important. The interaction between invasive plants and native plants is crucial. Several invasive plants contain unique compounds that are highly toxic to native plants (Callaway and Ridenour, 2004; Chengxu et al, 2011). Phytotoxicity or allelopathy or both are considered to be important for invasive plants to become naturalized in new habitats (Meiners et al, 2012)

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