CHEMICAL COMPOSITION AND ALLELOPATHIC EFFECT OF THE ESSENTIAL OIL OF ARTEMISIA HERBA-ALBA ASSO. ON SEED GERMINATION AND EARLY SEEDLING GROWTH OF LEGUMES AND GRASSES SPECIES

There is some evidence that allelopathic interference on the establishment of plants can be attributed to the effect of essential oils from Artemisia herba-alba. For this purpose, chemical composition essential oil and allelopathic effects of Artemisia herba-alba were evaluated to determine inhibitory or stimulatory effects of essential oils on seed germination and early seedling growth of two legumes (Medicago saliva L. and Onobrychis sativa Lam.) and three grasses (Lolium perenne L., Secale montanum Guss. and Bromus tomentellus Boiss.) in a laboratory experiment. The essential oils of aerial parts of Artemisia herba-alba were obtained by steam distillation and analyzed by GC-MS. Seed germination test was carried out on filter paper moistened with 5 ml of dilutions of essential oil or distilled water as control. The results showed that increased essential oil concentration reduced root lengths in Medicago sativa, Onobrychis sativa and Bromus tomentellus. Also, The effects of essential oil concentrations on seed germination show a tendency of being stimulatory effect at lower concentrations (300ppm, 500ppm) in S. montanum and inhibitory at higher concentration (700ppm) in all species except O. sativa. Percentage and speed of germination decreased with increasing essential oil concentration in grasses. However, no significant effect was seen on the two legumes species. GC MS studies revealed that The major compounds were cis-pinocarveol (17.5%), artemisia ketone (13%), trans-sabinene hydrate (8.5%), 1,8-cineole (8%) and aromadendrene (4.7%). Oxygenated monoterpenes constituted the major fraction of the essential oil in Artemisia herba-alba. Generally, Artemisia herba-alba shows allelopathic activity with increased essential oil concentration, which was more effective on seed germination and seedling growth of grasses.