摘要: Medicinal plant are grown and produced in different ecosystems and sites under the influence of different potential factors,including the altitude as one of the vital determinants in the quantity and quality of the plants.One of the species that grows in the highlands is Tanacetum polycephalum,an aromatic perennial of the Asteraceae.This species is characterized to be antiseptic,analgesic,anesthetic,disinfective,expectorant,anti-cancer,anti-allergic,and conducive to low blood pressure.The purpose of this study is to investigate the essential compositions in the aerial parts of T.polycephalum at the time of flowering,and in three different altitudes of the Baladeh region of Nour.Thus,the essential oil was extracted from the aerial parts in the flowering stage of the plant at three altitudes of 1 600,2 400 and 3 200 m using a water distillation method,and the essential oil compositions were identified using GC and GC/MS instruments.One-way ANOVA method was conducted to analyze the obtained data using SPSS,and a Duncan test was administered to compare the means.The results indicated that the essential output obtained from the altitudes of 1 600,2 400 and 3 200 m was(0.74±0.01)%,(1.09±0.02)%,and(1.32±1.2)%,respectively,so that the altitude of 3 200 m revealed the greatest quantity,and the altitude of 1 600 m represented the smallest quantity.Moreover,the essential oil compositions showed the highest percentage in the altitude of 3 200 m and the lowest percentage at the altitude of 1 600 m.The results showed that as the altitude increases,the essential oil compositions revealed the greater quantity and percentage in the aerial parts of T.polycephalum.