Effects of Fertilizer Treatments on Antioxidant Activities and Physiological Traits of Basil (Ocimum basilicum L.) under Water Limitation Conditions

Drought stress is a major environmental stress that restricts plant growth and production in the majority of agricultural fields of the world. The application of different fertilizers, especially biofertilizers and organic fertilizers, might play an important role in the production of medicinal plants in order to improve their resistance to deficit water stress. In order to evaluate the effects of fertilizer treatments on antioxidant enzyme activity and physiological characteristics of basils (Ocimum basilicum L.) under water-limited conditions, a study was arranged as a factorial layout based on a randomized complete block design with three replications. Two irrigation intervals (6, and 12 days) and six fertilizers levels [chemical fertilizers (N, P, K), vermicompost + mycorrhizal fungi (Glomus intraradices), vermicompost (10 t  ha-1)+bacterial biofertilizer [Azetobarvar1 (Azotobacter vinelandii as nitrogen-fixing bacteria), Phosphatebarvar2 (Pseudomonas putida and Bacillus lentus as phosphorus solubilizing bacteria), Pota barvar-2 (Pseudomonas koreensis and Pseudomonas vancouverensis as potassium releasing bacteria)], bacterial biofertilizer+mycorrhizal fungi, chemical fertilizers 50% (Basic NPK fertilizer was applied at the rate of 90–120–100 kg/ha in the form of urea, triple super phosphate, and potassium sulfate, respectively)+ bacterial biofertilizer and control] were assigned to the main plots and sub-plots, respectively. The results showed that water limitation decreased the chlorophyll content and relative water content, but carotenoids and antioxidantenzyme activities (catalase, superoxide dismutase, and peroxidase) and also osmolytes (proline and sugar) contents were increased. But, the application of fertilizer sources alleviated the drought effects, so the application of fertilizers (especially chemical fertilizers 50% + bacterial biofertilizer) increased these traits at all irrigation levels. Overall, in addition to cellular mechanisms, such as osmoregulation and antioxidant defense, fertilizers sources application can improve antioxidant activities and physiological traits of basil under water-limited conditions.