Effect of irrigation frequency on yield and chemical compositions of Salvia officinalis L. essential oil

Drought stress is as one of the most important limited factors that in agriculture systems can cause damage to growth, yield and secondary metabolites in medicinal and aromatic plants. A filed experiment to study on effect of irrigation frequencies, including 4, 6, and 8 every days on quantity and quality of the essential oil from the aerial parts of sage (Salvia officinalis L.) was done based on a randomized complete block design (RCBD) in three replications at the research field at Islamic Azad University of Shahrekord, southwestern Iran in 2016. The leaves of plant samples were harvested at early flowering stage and the essential oils were obtained by  hydro distillation by using the Clevenger-type apparatus d by GC/MS. Results indicated that irrigation frequencies levels had significant effects on essential oil yield and percentages of 1,8-cineole (as the main constituent in the oil), limonene and α–humulene. The highest yield oil and the maximum contents of 1,8-cineole (11.05%), limonene (2.67%) and α–humulene (1.32%) were obtained from treatment of eight every days of irrigation. Probably, it seems that increased irrigation intervals (mild drought stress) can be effective in quantitative and qualitative properties of essential oil from sage (Salvia officinalis L.).