Increased Medicinal Contents of Purslane by Nitrogen and Arbuscular Mycorrhiza under Drought Stress

Worldwide, purslane (Portulaca oleracea L.) is well-known for its fatty acids and antioxidants. To investigate interaction effects of nitrogen and mycorrhiza under water deficit stress on agronomic and medicinal traits of the purslane, a factorial split experiment based on a randomized complete block design with three replications was conducted in a semi-arid region of Iran in 2015 and 2016. The main plots were factorial combination of two irrigation conditions (non-stressed control and stressed condition: irrigation at 70% and 50% of field capacity (FC), respectively) and two treatments, i.e. control and inoculation with arbuscular mycorrhiza fungi (AMF, Rhizophagus irregularis). The subplots consisted of unfertilized control, 100% farmyard manure (8.5 mg FYM ha(-1), sheep manure (50%) and chicken manure (50%)), 100% N (120 kg urea ha(-1)), 75% FYM and 25% urea, 50% FYM and 50% urea, 25% FYM and 75% urea. In the first and second years, drought stress reduced AMF colonization (by 30.3% and 15.3%), phosphorus content (by 5.8% and 7.7%), nitrogen content (by 11.91% and 8.63%), total antioxidant capacity (by 16.7% and 14%), and biomass matter (by 21.1% and 17%) in purslane, respectively, while contributing to the production of malondialdehyde, total flavonoid, saturated and unsaturated fatty acids. AMF treatment increased the biomass weight, total antioxidant activity, and unsaturated fatty acid content of leaf in purslane. Application of nitrogen fertilizers enhanced phosphorus and nitrogen uptakes, biomass weight, flavonoid content, total antioxidant capacity, and fatty acid contents of the leaf under both irrigation conditions, while lowering leaf malondialdehyde content.