Abstract
Allelopathy has been regarded as a mechanism for the successful exotic plant invasion, but this mechanism has not been evaluated for Argemone ochroleuca Sweet; an invasive weed in rangelands and farmlands of the Arabian Peninsula. We investigated whether wild native range plant species (Farsetia aegyptia Tuna and Salvia aegyptiaca L.) and forage crops (Hordeum vulgare L. and Medicago sativa L.) respond differently to potential allelopathic effects of aqueous extracts from roots and shoots of A. ochroleuca growing in two habitats; rangelands and farmlands. Almost all the germination indices were sensitive enough to establish the allelopathic potential of aqueous extracts. Inhibition of seed germination of the test species showed species-specific; concentration, organ and habitat dependent response with highest inhibition occurring at 100% concentration of shoot extract from rangeland habitat. Seed germination of F. aegyptia was the most sensitive to different aqueous concentrations extracted from the two habitats, whereas H. vulgare seed germination was the least sensitive. The results suggest different organs of A. ochroleuca exhibit sufficient allelopathic potential in different habitats.