Screening of allelopathic invasive plants in Japan and East Asia
Yoshiharu FUJII
Tokyo University of Agriculture and Technology, Tokyo, Japan
Exotic plants threaten the integrity of agricultural and natural systems throughout
the world. Many invasive species are not usually dominant in their native regions,
but once they invaded into new regions, they competitively suppress the growth
of their new neighbors. Callaway and his colleague published many papers demonstrating
the importance of allelopathy of dominating invasive alien plants in North America
and coined "Novel weapons hypothesis" (Science 2000). We have developed
specific bioassay systems for allelopathy, named "Sandwich Method", "Plant Box Method", and
"Dish-pack Method". By using these methods, we have
done screening in Japan and surrounding countires and found some of the invasive
plants are allelopathic. Some of allelochemicals were isolated. Among these
plants, several examples of allelochemicals from alien plants in Japan will be demonstrated:
1) Leucaena leucocephala: an invader to tropical and subtropical island has
an unusual amino acid, mimosine, isolated as the major allelochemical in this
leguminous tree;
2) Bishofia javanica: native to south east Asia, but now becoming an invader in
Ogasawara Island, has tartaric acid as allelochemicals;
3) Prosopis juliflora: leaching of the allelopathic substance, L-tryptophan from the
foliage of this mesquite was demonstrated. Juliflorine, a unique alkaloid, was also
detected as major allelochemical;
4) Other invasive alien plants with potent allelopathic activity are: Coccinia grandis,
Rottboellia cochinchinensis, Fumaria capreolata, Phalaris brachystachys, Physalis
angulata, Gypsophila paniculata, Oenothera hookeri, Trifolium incarnatum, Ipomopsis
rubra, Silene armeria, Avena strigosa and, Anisantha madritensis.
Estimation of their invasion and toxicity to the environment, and the potential allelochemicals
will be discussed. We would like to have cooperative research on the
screening of allelopathic plants from East Asian Flora.
© 2012 Organizing Committee
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