Arizona cypress is a major urban landscape tree many of which have declined in the recent years. Although the cause for this decline is complicated, drought, heavy toxic metals such as cadmium and air pollution are generally thought to be leading factor. This research was conducted in three different studies. In the first study, we designed an experiment to investigate the effects of artificial inoculation of seedlings of a major urban forest tree, Arizona cypress ( Cupressus arizonica Green) with beneficial microorganisms under the water stress. The results clearly showed that SWD adversely affected root colonization, morphological parameters, relative water content, and soluble carbohydrate content. However, antioxidant enzyme contents (i.e. catalase, superoxide dismutase, glutathione peroxidase, ascorbate peroxidase), hydrogen peroxide, malondialdehyde, and proline increased as a result of water stress. Dual-inoculated plants with both AMF and PF inoculation accumulated more ascorbate peroxidase and glutathione peroxidase than plants with merely PF or AMF inoculation under SWD conditions. Dual-inoculated plants significantly decreased the water deficit-induced hydrogen peroxide and malondialdehyde in Arizona cypress leaves. Both AMF and PF inoculation positively improved plant biomass compared with control under different irrigation regimes. Moreover, AMF inoculation improved GRSP concentrations by 24% but, it was not statistically significant. Nutrient uptake was negatively affected by WD, especially in control plants. Both AMF and PF inoculation increased nutrient uptake (except for zinc) compared with control. In conclusion, the symbiotic association between PF and AMF can alleviate water-deficit damage and improve water stress tolerance in the Arizona cypress. In the second study, we conducted an experiment as a factorial experiment based on a completely randomized design with three factors comprising AMF inoculation [( R. irregularis or F. mosseae or a mixture of both species, or non-inoculated controls (Non-AMF)], bacterial inoculation ( P. fluorescens or non-inoculated), and five levels of cadmium (0 or 5 or 10 or 15 or 20 mg kg-1) using three replications on Arizona cypress. Based on the results of this study, Arizona cypress growth was clearly decreased when exposed to the high levels of cadmium (Cd) contamination (15 and 20 mg kg-1). However, dual inoculated plants grown under the highest levels of Cd contamination, showed increased photosynthetic pigment concentrations and elevated superoxide dismutase and ascorbate peroxidase activities. Moreover, high levels of Cd contamination negatively influenced phosphorus uptake by the plants, especially in non-inoculated plants. Moreover, in AMF inoculated plants the accumulation of Cd was less, apparently as a result of AMF modification of the influx of Cd into the host plants. This was confirmed by reduced hydrogen peroxide and enhanced antioxidant enzyme activities compared to the non-AMF plants. In conclusion, Arizona cypress responded properly to AMF inoculation under Cd stress conditions, where PF found to be less effective. The third study, was designed to investigate the effects of artificial inoculation of seedlings of Arizona cypress with beneficial microorganisms under the stress of air pollution caused by exhaust emissions from fuel pollutants (FP). We conducted this research as a completely randomized design in a form of split-factorial with three factors comprising AMF inoculation with R. irregularis or F. mosseae or a mixture of both species, bacterial inoculation with P. fluorescens and non-inoculated controls, and two levels of FP (fuel pollutants and non-fuel pollutants) using three replications of each treatment. Fuel pollutants significantly reduced root colonization, shoot and root dry weight, nutrient concentrations (N, P, K, and Fe), GRSP, and chlorophyll concentration, while increasing proline content, enzyme activity, malondialdehyde, and hydrogen peroxide concentrations in Arizona cypress seedlings. Nevertheless, adverse effects of FP in the inoculated plants (especially AMF plants) were less than in the non-inoculated plants. Inoculations of AMF especially the mixture of both mycorrhizal species effectively alleviated the negative effects of FP on Arizona cypress seedlings. This promising effect was related to increased GRSP content in the media which improved concentrations of N, P, and Fe in plants, enhanced chlorophyll concentration, and elevated enzymatic antioxidants such as ascorbate peroxidase and glutathione peroxidase which resulted in increased dry mass of the plants under air pollution stress. Keywords Air pollution, Antioxidant Enzymes, Evergreen tree, Funneliformis mosseae , Glomalin, Heavy metal, Nutrients, Pseudomonas fluorescens , Rhizophagus irregularis , Water stress.