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The rising demand for guava fruit worldwide is due to its richness in vitamin C, high yielding and two bearing seasons. Given the salt stress threat to guavas and the necessity of protective strategies, in the present research guava seedlings were subjected to sodium chloride (0 and 50 mM) and salicylic acid (0 and 1 mM). To ascertain a logical conclusion, the activity of antioxidant enzymes, antioxidant capacity of DPPH, ferric reducing antioxidant power, total flavonoid and phenol contents were monitored in saltexposed guava seedlings. Based on our findings, the most superoxide dismutase (87.46 µmol min −1 g −1 DW) activity, ferric reducing antioxidant power (408.82 mmol g −1 DW), DPPH scavenging activity (80.65%), flavonoid (14.15 mg QE −1 g DW) and phenol (34.02 mg GAE g −1 DW) contents were found in 50 mM NaCl-exposed plants, which were enriched by 1 mM salicylic acid. A high correlation was observed among non-enzymatic antioxidant parameters (DPPH scavenging activity, ferric reducing antioxidant power, total flavonoid content and total phenol content). In conclusion, salicylic acid improved guavas salt tolerance by increasing both enzymatic (peroxidase and superoxide dismutase) and non-enzymatic (ferric reducing antioxidant power, DPPH scavenging activity, total phenol and flavonoid contents) pathways.

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In order to investigate the effect of mycorrhizal arbuscular fungi (MAF) and vermicompost on drought tolerance of Mexican Lime seedlings (Citrus aurantifolia cv. Mexican Lime), a factorial experiment was conducted as a completely randomized design in greenhouse conditions. Factors included were water stress at three levels (100% ET c , 70% ET c and 40% ET c ) and biofertilizers at three levels (0, 100 g mycorrhiza, 100 g vermicompost per pot) with four replications. Irrigation treatments were applied for two months on one year seedlings. The results showed that growth of leaf and root was significantly affected by drought stress and decreased, whereas the effect of drought stress on fresh and dry weight of stem was not statistically significant. According to the results, the rate of decrease in fresh and dry weight of leaves under severe water stress treatment compared to full irrigation was 35.38 and 31.79%, respectively. Also, the rate of decrease in fresh and dry weight of root in severe water stress treatments was 35.53 and 34.11%, respectively, compared to full irrigation. Inoculation of seedlings with bio-fertilizers especially 100 g mycorrhiza per pot significantly increased leaf fresh weight (19.94%), leaf dry weight (17.31%), stem fresh weight (26.7%), stem dry weight (26. 1%), root fresh weight (35.53%), root dry weight (14.82%), RWC (76.19%), enzyme activity, chlorophyll a -(0.637 mg.g f.w.), b (0.372 mg.g f.w.) and carotenoid (11 mg.g f.w.) and reduced ion leakage (62.5%) compared to non-inoculated seedlings. Based on the results, it can be stated that application of 100 g bio-fertilizer could reduce adverse effects of drought stress on the Mexican Lime seedlings.