To investigate the effect of organic fertilizers on the quantitative and qualitative characteristics of sugar beet under different moisture conditions, a study was conducted as a split plot experiment based on a randomized complete block design with three replications in Mahabad city in 2021. Irrigation treatments, including irrigation after 60 (normal), 90 (mild stress), and 120 (severe stress) mm evaporation from the class A evaporation pan, and organic fertilizer treatments (control, vermicompost, manure, and humic acid) were placed in main plots and sub-plots, respectively. Severe water stress conditions reduced the content of chlorophyll a (22.82 %) and relative water content (RWC) (24.35 %) and increased the content of proline (47.43%), beta glycine (17.89%), catalase (21.30 %), malondialdehyde (47.95 %) and water use efficiency (WUE) (23.83%) compared to normal irrigation conditions. Also, the application of vermicompost increased the amount of chlorophyll a, RWC, proline, glycine beta, catalase content, and WUE by 29.11, 20.15, 34.83, 14.98, 13.70, and 21.56 percent, respectively, and decreased the content of malondialdehyde about 18.53% in comparison to control. In this study, the highest stomatal conductivity (51.01 mol.m-2s-1), chlorophyll b content (16.3 mg.g-1FW), carotenoid (4.27 mg.g-1 FW), roots yield (78.33 t.ha-1) and the lowest content of hydrogen peroxide (0.96 μmol.g-1FW) allocated to the vermicompost treatment under normal irrigation conditions. Root yield showed a positive and significant correlation with stomatal conductance, chlorophyll b, carotenoid, RWC, and WUE, but a negative and significant correlation with catalase enzyme activity, hydrogen peroxide content, malondialdehyde, and sugar content.

n order to investigate AMF and phosphorus fertilizer effects on bitter gourd under different irrigation regimes, an experiment was conducted in the research farm of the faculty of agriculture of Tarbiat Modares university in 2020 as a split factorial based on a randomized complete blocks design with three replications. Three irrigation regimes including full irrigation, moderate irrigation deficit, and severe irrigation deficit were randomized in the main plot units and the factorial combination of two species of fungi Glomus mosseae and Glomus intraradices along with control (without fungi) and an amount of phosphorus with a control without phosphorus was randomly placed in the sub-plot units. The results showed that under water dificit stress, fruit yield, total chlorophyll, leaf phosphorus, and colonization percentage decreased compared to full irrigation, and proline, MDA, leaf ion leakage, CAT and APX enzymes, and coumaric acid increased. The use of AMF and phosphorus fertilizer under full and low irrigation conditions reduced MDA and improved fruit yield and the other investigated plant traits. The highest fruit yield (3133.27 g.m-2) was allocated to the plants under inoculation with Glomus mosseae species and phosphorus application under full irrigation regime. The highest amount of fruit coumaric acid (almost 11 ppm) was obsereved in inoculated plants with Glomus mosseae species and application and non-application of phosphorus fertilizer under severe irrigation deficit. According to the obtained results, it is possible to suggest the use of two species of Glomus mosseae and Glomus intraradices and sufficient phosphorus element to improve the yield and quality of bitter gourd fruit under water dificit stress and full irrigation.