Effects of arbuscular mycorrhizal fungi and harvesting time on the macro- and micronutrients and antioxidant enzymes activity of thyme (Thymus Vulgaris L.) in the different irrigation levels

In order to evaluation the effects of arbuscular mycorrhizal fungi (AMF) and harvesting time on the macro- and micronutrients and antioxidant enzymes activity of thyme (Thymus Vulgaris L.) in different irrigation levels, a field experiment study was carried out as Split plot in time and place with 12 treatments and three replications at the faculty of Agriculture, University of Maragheh, Iran, in 2019. The first factor was three irrigation levels included irrigation after depletion of 20% maximum allowable depletion (W20), depletion of 50% of maximum allowable depletion (W50) and depletion of 80% of maximum allowable depletion (W80) as severe stress. The sub factor was application and non-application of mycorrhiza and sub sub factor was harvesting time (first and second harvest). The results demonstrated that the highest and lowest content of N, P, K, Zn, Fe and Ca was observed in W20 and W80 irrigation levels, respectively. Also, with application of AMF, the content of N, P, K, Fe, Zn and Mn increased by 17.4, 24.7, 20.9, 20.6, 11.8 and 18.2% compared with untreated control. Among different irrigation levels, the highest content of Chlorophyll a (0.8 mg/g fresh weight), b (0.48 mg/g fresh weight) and total (1.28 mg/g fresh weight) was achieved in the non-stress conditions (W20). Also, the highest antioxidant enzymes activity such as superoxide dismutase, ascorbate peroxidase and guaiacol peroxidases was achieved in the moderate and severe water stress conditions with application of AMF. Generally, the results showed that application of AMF play a main role in improving plant nutrient absorption and increasing resistant to drought stress conditions.