Allelopathic Potential of Common Thistle (Cirsium japonicum) Leaf Extracts and Residues

Common thistle(Cirsium japonicum) is known to contain water-soluble substances that are biologically active. Aqueous extracts, methanol extracts and residues from leaves of common thistle were assayed to determine their allelopathic effects, and allelochemicals from various fractions were quantified and assayed. The aqueous extracts significantly inhibited seed germination and root growth of alfalfa(Medicago sativa L.). Root growth of alfalfa was completely inhibited by leaf extracts of 40g , while root growths of barley(Hordeum vulgare L.) and soybean(Glycine max L.) were less sensitive to the extracts. The effect of residue incorporation into soil was examined in a greenhouse, and the leaf residues at 100g inhibited shoot and root fresh weights of barnyardgrass by 88 and 84%, respectively. By means of HPLC analysis, the major phenol compounds identified and quantified were coumarin, trans-cinnamic acid, and chlorogenic acid. Of them, trans-cinnamic acid was found as the greatest amount(20.9mg dry weight) at ethylacetate fraction. Methanol extracts from hexane and ethylacetate fractions of common thistle reduced alfalfa root growth more than did those from butanol and water fractions. These results show that extracts from common thistle leaves have herbicidal potential, and that its activity exhibited differently depending on type and amount of causative compounds by fraction