Biochemical changes of peppermint under drought stress condition

The Cultivation of medicinal plants such as Lamiaceae family increasing throughout the world significantly. Peppermint consider as an important species in this family which it’s important is due to menthol in essential oil. In this study the physiological and biochemical responses of peppermint investigated under different levels of irrigation including 100 (as control), 75, 50 and 25 % field capacity (FC) in CRD design with three replications in research greenhouse of Agronomy Department of University of Tehran in 2013. The results of Anova indicated that, irrigation levels had high significant effect (P≤0.01) on H2O2, MDA, CAT, APX, GPX and SOD. While, the effect of irrigation levels was not considerable on soluble sugar content. The highest content of soluble sugar and soluble protein were observed at 50 and 75 % FC, respectively. The highest H2O2 and MDA (59.63 and 16.25 µmol/g) observed at 25% FC with significant difference in respect to other treatments. The highest activity of antioxidant enzymes CAT, APX and GPX detected at 50 % FC and reduced with increasing of drought stress up to 25 % FC. The activity of SOD increased with increasing of the drought stress and reaching it to maximum amount at 25 % FC. These results suggest that peppermint is a sensitive plant and cannot increase its capacity against drought stress.