Compositae plants are known to contain biologically active substances that are allelopathic to agricultural crops as well as weed species. Aqueous extracts from leaves of Xanthium occidentale were assayed against alfalfa (Medicago sativa) to determine their allelopathic effects, and the result showed that the extracts applied onto filter paper significantly inhibited seed germination as well as root growth of alfalfa. Untreated seeds germinated in 60h, but extract concentrations greater than 30g ~textrmL-1 delayed seed germination. The extracts significantly inhibited seed germination of alfalfa, and β -amylase activity of alfalfa and barley seeds during 24-36 hours after treatment. Aqueous extracts of 40 g ~textrmL-1 from X. occidentale were completely inhibited the hypocotyl and root growth of alfalfa. Aqueous leaf extracts showed the highest inhibitory effect and followed by root and stem extracts. Early seedling growth of both alfalfa and barnyard grass (Echinochloa crus-galli) was significantly reduced by methanol extracts. By means of high-performance liquid chromatography, chlorogenic acid and trans-cinnamic acid were quantified as the highest amounts from water and EtOAc fractions, respectively. BuOH and EtOAc fractions of X. occidentale reduced alfalfa root growth more than did hexane and water fractions. The findings of the bioassays for aqueous or methanol extracts reflected that the inhibitory effect of extract was closely related to the level of responsible allelochemicals found in plant extracts.

들깨 및 메밀 건경의 물 추출액을 피 및 배추에 처리하여 발아 및 초기생장의 억제 양상을 본 결과 1. 두가지 추출액 모두 피와 배추의 발아를 억제하였으며 메밀 추출액이 들깨 추출액보다 심하였고 피보다는 배추에 억제효과가 켰다. 2. 발아후 초기 생장도 위와 같은 경향이나 발아억제보다는 생장 억제 효과가 약간 적은 영향이었다. 3. 이들 추출액은 지상부 생장보다는 뿌리 생장에 피해를 더 주는 경향이며 들깨 추출액보다 메밀 추출액이 더 심한 편이었다.