Alteration of antioxidant enzymes of forest savory (Satureja mutica) under ‎the influence of drought stress, re-watering and selenium foliar application

Climate change and rainfall patterns pose a serious ‎threat to the world's food supply to a growing population. Water scarcity is ‎currently limiting food security and economic prosperity in many parts of the ‎world. One of the solutions of the increasing the water productivity is ‎cultivation of the drought-resistant medicinal plants. Forest savory is one of ‎the native medicinal plants of Iran, which contains valuable medicinal and ‎chemical compounds. The aim of this study was to investigate the trend of ‎changes in antioxidant enzymes of two forest savory chemotypes under ‎drought stress conditions, re-watering and selenium foliar application.‎

‎In the present study forest savory chemotypes of “carvacrol/thymol/p-‎Cymene” (Darkesh chemotype) and “thymol/p-Cymene/carvacrol” (Pono ‎chemotype) with herbarium code of MPH-1347 were used. The experiment ‎was conducted in the form of a split plot experiment based on a randomized ‎complete block design. Drought were applied at 3 levels (control, moderate ‎stress (25 days without irrigation) and severe stress (40 days without ‎irrigation). selenium treatments was applied at 3 levels (0, 5 and 20 mg) as ‎foliar application. Re-irrigation was performed immediately after drought ‎stress. In order to measure enzymatic activity variation of plant 3 stages the ‎sampling was done. Including: at the end of drought stress of each treatments, ‎‎1 day and 5 days after re-watering.‎

Re-irrigation acts as a mechanism to restore physiological functions ‎that have been reduced by water stress. In other words, recovery is an ‎important component for adaptation of plants. In present study, drought stress ‎was not significantly altered the enzymatic activity of measured antioxidant ‎enzymes (except catalase in “Peno” chemotype) in both chemotypes. There ‎was also no significant reaction to selenium foliar application in different ‎levels. On the other hand, the study of changes in enzyme activity before and ‎after re-irrigation showed that, although the enzyme activity tended to reduce ‎after re-irrigation, but in the shortest possible time the activity of enzymes ‎reached to pre-irrigation conditions indicates the high resistance of this plant ‎species to drought. Also, the plant's response to drought levels and supportive ‎treatments in the two chemotypes had almost the same trend.‎

The lack of response of important antioxidant enzymes of forest ‎savory to drought stress and supportive treatments stated that this plant as a ‎drought-tolerant plant containing is suitable for cultivation in areas with ‎limited water resources and irregular rainfall. Therefore, it is suggested that ‎this plant be used for cultivation in low water conditions of Shahrood and ‎similar areas.‎