Allelopathic effects of aqueous and residue of different weeds on germination and seedling growth of wheat

The allelopathic effects of six weeds including Conyza bonariensis، Acroptilon repens، ­Artemisia annua، Inula graveolense، Solanum nigrum and ­Xanthium strumarium­ on seed germination and seedling growth of wheat was investigated using a complete randomized design with three replication in laboratory and glasshouse of college of agriculture، University of Gorgan in 2009. The result showed that shoot extracts of Xanthium strmarium، Acroptilon repens and Conyza bonariensis significantly reduced germination rate of wheat in 47، 42 and 25 percent، respectively. Also، shoot and root extracts of these three plants reduced coleoptile length، root length، and root dry weight of wheat seedlings. Roots appeared more sensitive than shoots respective to allelopathic effects. Aqueous extracts were more phytotoxic than dried plant extracts and also shoot extracts had higher detrimental effects than root extract. In general، shoot extracts and residue of three plants mentioned، significantly reduced germination، root length، shoot length and root dry weight of wheat seedlings. Therefore، extract of Acroptilon repens might contain numerous growth inhibitors that could be used for the development of biological herbicides.