Study of allelopathic effect of Artemisia herba alba Asso. on seed germination and seedling growth of Onobrychis sativa L. and Medicago sativa L

Allelopathic compounds influence biochemical and physiological processes of their adjacent plants. Artimisia herba alba is a shrub and perennial plant which has widely distributed in Iran rangelands Allelopathy effects of different concentratins of essentioal oils of the species on germination percentage, speed germination and growth parameters (root and shoot lenght, fresh and dry weight) of Medicago sativa and Onobrychis sativa were studied. The concentrations were 100, 300, 500 and 700 ppm compared with distilled water as control treatment. ED50 and ED90 values were calculated using dose response curves for Not-germinated (probit scale) against essential oil concentration (log scale). Results showed significant differences between the treatments on root length and vigor index at 0.01 probability level, shoot length, and fresh weight at 0.05 probability level. The treatment level of 700 ppm showed the lowest root length, fresh weight and vigor index. Thirty two combinations were identified by gas chromatography in which cis-pinocarveol and artemisia ketone showed the highest level. Increment of the essential oil concentrations decreased seedling growth parameters and germination percentage in Medicago sativa and Onobrychis sativa. It seems cis –pinocarveol as terpens composition and artemisia ketone, trans-sabinene hydrate, 1,8-cineole and Myrcene as monoterpene compositions, that constituted a high percentage of the essential oil of the species, have a major role in the development of allelopathic effects of Artimisia herba alba.