J. Weed Sic. Tech Vol. 42 (1) 31-35 (1997) 雑草研究 Short Report Exudation of Allelopathic Compound from Plant Roots of Sweet Vernalgrass (Anthoxanthum odoratum) Yoshito Yamamoto** and Yoshiharu Fujii*** KeyWords: Anthoxanthum odoratum, allelo- chemicals, root, exudation, coumarin. キー ワ-ド: ハ ル ガ ヤ,ア レ ロ パ シー 物 質,根, 滲 出, ク マ リン Introduction Several studies have been conducted on the allelopathy of sweet vernalgrass (Anthox- anthum odoratum)10,11), and Yamamoto17) iso- lated and identified coumarin as an al- lelopathic compound produced by A. odor- atum. It has been reported that coumarin is present in all parts of this plant, and is partic- ularly highly concentrated in the leaves, accounting for more than 2.5% of dry leaf weight in June17). Yamamotol8) indicated that coumarin of the A. odoratum plant residue easily moves into the soil after rainfall where both soil type and the presence of micro- organisms are related to its disappearance. Evidence also indicated that allelopathic compounds come from plants by volatiliza- tion, decomposition of residues, exudation from roots or by leaching during rain14). Many kinds of plant root exudates are report- ed15), and Rice14) indicated that evidence was quite strong that many identified allelopathic compounds and other related compounds were exuded from plant roots, taken up by neighboring plants, and cause growth changes in the receptor species. The concen- tration of these compounds exuded from plant roots determined to estimate their al- lelopathic potential5). This assessment is diffi- cult, however, Tang and Young16) developed an excellent technique using XAD-4 resin to collect exudates from roots of plants, and identified 16 allelochemicals in the root exudate of Hemarthria altissima. In this experiment, we applied the new "Plant Box Method" developed by Fujii and Shibuya6) to determine the concentration of allelopathic compound exuded from the root of A. odor- atum. The principle of this method involves assessing the effect of root exudates of the living donor plant by soaking its root in agar medium and mixed culture in the same medium in a plant box for tissue culture6,7). Fujii7) tested more than 250 species with this technique and indicated that the activities of several species were prominent. The purpose of the experiments reported here was to investigate the exudation of allelopathic compound from the roots of A. odoratum using this Plant Box Method, and to assure that the exuded compound has the potential to impact the plant species sur- * This study was supported in part by a Grant-in- Aid (Bio Cosmos Program) from the Ministry of Agriculture, Forestry, and Fisheries (BCP97-II-A -1). ** Department of Ecology, National Grassland Research Institute, Nishinasuno, Tochigi 329-27, Japan. Present address: Department of Grass- lands, Kyushu National Agricultural Experiment Station, Nishigoushi, Kumamoto 861-11, Japan. *** Department of Environmental Biology, National Institute of Agro-Environmental Sciences, Tsu- kuba, Ibaraki 305, Japan. (Accepted September 30, 1996) 山 本 嘉 人**・藤 井 義 晴***: ハ ル ガ ヤ(Anthoxanthum odomtum)根 か らの ア レロパ シー物 質 の滲 出. **草地 試 験 場(現 在: 九州 農 業 試 験場), ***農業環境技術研究所