effect of drought stress on some physiological properties and antioxidant activity of achillea tenuifolia lam.

background & aim: osmotic stress in plants lead to increase free radicals and plants use different mechanisms to scavenge these radicals. so, researchers apply stresses especially drought stress to increase secondary metabolites such as phenolics, and antioxidants. one of the valuable medicinal plants is yarrow (achillea tenuifolia) which is a perennial plant with different medicinal applications. experimental: in order to assess the effect of drought stress, four different treatments (25%, 50%, 75% and 100% of field capacity) with four replicates was done in plastic pots at greenhouse. after 30 days, leaves of samples were used to evaluate total phenolics, antioxidant activity using three model systems including 1,1-diphenyl-2-picrylhydrazy (dpph), ferric thiocyanate (ftc), and β-carotene-linoleic acid assay. in addition, malone dialdehyde (mda), and proline content were evaluated. results & discussion:  drought stress in a.tenuifolia significantly increased total phenoloics, and antioxidant activity (in dpph and β-carotene-linoleic acid assay).  in addition, proline and malone dialdehyde were elevated by stress, while according to ftc model, there was no significant differences between 25% and 50% fc treatments. industrial and practical recommendations: according to the results of present study, the 50% fc treatment can be introduced as acceptable drought level to produce sufficient phenolics and acceptable plant yield. finally, more studies suggested for assessing the effect of drought stress on amount of other compounds in this medicinal plant.