identification of some ecological factors affecting essential oil of verbascum songaricum schrenk shoots (case study: rangelands of isfahan and kohgiluyeh and buyerahmad provinces, iran)

the effect of environmental factors on plant vegetation is different. therefore, it is necessary to evaluate role of these factors in medicinal plants growth, development and essential oil. this study was performed to investigate the effect of factors on qualitative and quantitative variations of the essential oil of verbascum songaricum in its habitats in central zagros mountains, iran in 2012. v. songaricum aerial biomass was collected in flowering stages from four rangeland sites in isfahan (dareh hose, ghahiz, ghaleghadam, semirom) and one site in kohgiluyeh, and buyerahmad (dena) provinces, iran. the samples were dried in open air and their essential oils were extracted through digestion method. gas chromatography mass spectroscopy (gc-ms) was used to identify essential oil composition as alcohol, hydrocarbon, amin, acid, ester and ketone of species in five sites. the most important environmental factors such as climate, and physiographic, soil physical and chemical properties were determined. in order to investigate the relationship between environmental factors and plant essential oil, ordination analysis was performed using redundancy analysis (rda). the results of correlation analysis indicated that the most important environmental factors affecting the essential oil were annual rainfall (r=0.86), frozen days (r=0.86), aridity index (r=0.86), altitude (r=0.86), gravel (r=0.74), nitrogen (r=0.78), organic matter (r=0.62) and soil texture (r=0.68). results showed that there was an increase in essential oil production in v. songaricum under semi-arid cold climate, uplands, higher precipitation, relatively light texture and fertile soil. according to rda analysis, two habitats were identified. the first habitat was more appropriate for essential oil production of v. songaricum (dareh hose, semirom and dena) in comparison with the second one (ghahiz and ghaleghadam). as a result, the first habitat was considered as a suitable natural place for the cultivation and domestication of v. songaricum.