In arable soils, decreasing the fungal population due to tillage, application of chemical fertilizers and pesticides, reduces the potential benefits of mycorrhizal fungi for crop plants. To solve this problem, soil inoculation can be a practical ways to improve population size of mycorrhizal fungi, however, in this situation, weeds can also be benefited. This study aimed to evaluate the effect of three species of arbuscular mycorrhizal fungi (Funneliformis mosseae, Rhizoglomus fasciculatum, Rhizoglomus intraradices) on the growth of I.purpurea. Results indicated that inoculation with R. intraradices increased photosynthetic rate 1.9 times compared to control plants and inoculation with F. mosseae increased leaf chlorophyll index, root dry weight and root volume by 35%, 60 % and 70%, respectively, compared to the non inoculated plants. Inoculation with F. mosseae and R. fasiculatum improved plant growth parameters. Inoculation with AMF also increased plant's secondary metabolites, including phenolic compound, flavonoids and total terpenoid. The concentration of flavonoids in leaves of I. purpurea colonized by F. mosseae was 4.2 times more than that found in leaves of non- inoculated control plants. Increased photosynthesis, growth and secondary metabolites content in weeds associated with mycorrhizal fungi indicate that the competitive ability and allelopathic potential of these plants will increase when associated with AMF and the high allelopathic potential may facilitate this weed to become a good competitor against other plant species in the environment.