The physiology of mycorrhizal Lolium multiflorum in the phytoremediation of petroleum hydrocarbon-contaminated soil



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Arbuscular mycorrhizal fungi (AMF) can play an important role in the phytoremediation of petroleum hydrocarbon (PH)-contaminated soil. However, little is known about the effects of AMF in combination with biostimulation via fertilization or bioaugmentation with hydrocarbonoclastic microorganisms, during phytoremediation of PH in soils. This research evaluated the influence of the AMF Glomus intraradices and inorganic fertilization on growth and physiological responses of Lolium multiflorum Lam. cv. Passarel Plus during phytoremediation of soil contaminated with Arabian medium crude oil (ACO). Also determined was the interaction of AMF with the hydrocarbonoclastic bacterium, Sphingomonas paucimobilis EPA505 (Sp), and the filamentous fungus, Cunninghamella echinulata var. elegans ATCC-36112 (Ce), on growth and selected physiological responses of L. multiflorum during phytoremediation of soil contaminated with benzo[a]pyrene (BaP) or ACO. This research provides evidence that AMF enhance the phytoremediation of petroleum hydrocarbons in soils when inoculated with L. multiflorum. The concentration of petroleum hydrocarbons in soil was a determining factor of potential benefits of AMF on L. multiflorum. Low (3000 mg?kg-1) or high (15000 mg?kg-1) concentrations of ACO resulted in limited benefits of AMF on plant growth, physiology, and degradation of ACO in soil. However, when plants were exposed to an intermediate ACO concentration in soil (6000 mg?kg-1), AMF plants had enhanced growth, physiological responses, and greater ACO-degradation than non-AMF plants. The AMF symbiosis in roots of plants was observed at all concentrations of ACO-contaminated soil. This research is one of the first reports demonstrating the benefits of AMF on the degradation of benzo[a]pyrene or ACO, alone or in combination, with the hydrocarbonoclastic microorganisms. Thus, AMF resulted in a beneficial synergism with the hydrocarbonoclastic microorganisms, particularly during ACO-degradation in the rhizosphere of L. multiflorum. Hydrocarbonoclastic microorganisms had no negative effects on AMF colonization.