Comparison of drought on pigments, osmotic adjustment and antioxidant enzymes in different wild accessions of Anthemis tinctoria and Tripleurospermum servanes of Natural Resources Gene Bank of Iran

Drought stress is one of the most important factors limiting the survival and growth of plants in the Drought stress is one of the most important factors limiting the survival and growth of plants in the different habitats of Iran. Detailed knowledge about the ecophysiological responses of native plants to drought stress could contribute to the success of re-vegetation programs. Different accessions of two perennial chamomiles، Anthemis tinctoria and Tripleurospermum servanes were subjected to four drought treatments، i. e. well-watered (control)، mild drought stress (75% field capacity)، moderate drought stress (55% field capacity)، and sever drought stress (35% field capacity). Osmotic solutes (proline and soluble sugars)، Relative water content (RWC)، antioxidant enzymes (peroxidase and polyphenoloxidase) and pigments were investigated. Drought stress significantly increased accumulations of osmotic solutes، but decreased relative water content، total proteins content، dry matter percentage in the studied species. In both species the chlorophyll a and total chlorophyll contents did not changed in drought stresses، however the cartenoids content and the ratio of cartenoids to total chlorophylls significantly increased. Although the peroxidase activity، as an antioxidant enzyme، of all three accessions of T. servanes increased in sever drought stress، but in two accessions (of three accessions) A. tinctoria considerably decreased. These findings suggested that the A. tinctoria and T. servanes showed a moderate tolerance to drought، although in both species some accessions had higher tolerance to sever drought stress than the other accessions due to higher capacities of osmotic adjustment.