Physiological and Biochemical Evaluation of Achillea tenuifolia Lam. and A. vermicularis Trin. wild populations under drought stress

Five wild populations of Achillea tenuifolia Lam. (three populations from hot/dry and cold/dry climate regions) and A. vermicularis Trin. (two populations from cold/wet climate region), were subjected to drought stress in order to assess the levels of drought tolerance through the analysis of relative water content, leaf moisture percentage, osmotic solutes (proline and soluble sugars), antioxidant enzymes (peroxidase and polyphenol oxidase), soluble proteins content, and pigments content. Variation among populations under different levels of drought shows that populations are characterized by a different tolerance to drought. In A. tenuifolia, the hot/dry climate populations (T-Semnan and T-Sabzevar) had higher capacity of osmotic adjustment and antioxidant protection than the cold/dry climate population (T-Khalkhal). In A. vermicularis populations, from the same cold/wet climate region, V-Baneh2 vs. V-Baneh1 seems to be the most tolerant. These results showed that drought tolerance may be closely related with efficient photoprotective system, accumulation of osmoprotectants, and the increased capacity of the antioxidative system to scavenge reactive oxygen species.