en Epichloë Endophyte Modifies Antioxidative Defense and Aquaporin Genes Expression in Response to Ni Contamination in Lolium perenne تنش فلزات سنگین Toxic ions stress پژوهشي Research The aim of this study was to determine the impacts of endophyte (E) inoculation on Nickel tolerance of the <em>Lolium prenne</em> by measuring the physiological and biochemical traits in two populations of ryegrass consisting both (E-) and (E+) plants cultivated under Ni stress. The plants were grown in a Ni polluted soil at 0, 30, 90 and 180 mg Ni kg ^-1. The present research showed that the activity of antioxidant enzymes increased in Ni treated plants in contrast to control plants; whereas the activity of glutathione reductase enzyme decreased. Also, endophyte infection increased the activity of some antioxidant enzymes but decreased the activity of SOD enzyme. Upregulation of aquaporin gene (<em>LpTIP1;1</em>) was shown in population 1 E+ plants at all treatments and 30 ppm Ni in E- plants, whereas, the expression of <em>LpTIP1;2</em> in population 1 E- plants increased and no significant difference was shown for E+ plants. After 3 months from treating plants, considerable reduction in shoot biomass of E+ and E- plants was observed in 180 ppm Ni and endophyte inoculation decreased the biomass of plants. The shoot water content of E- plants was greater than E+ counterparts. A significant increase of Ni concentration of roots and shoots was also observed under Ni stress and the Ni concentration of E+ plants was 88.7% and 12.7% greater in shoots and roots, respectively, than in E- plants. Overall, results suggest that variation in response to Ni stress in E+ and E- ryegrass populations may aid survival of the grass under stress conditions. Keywords: Aquaporin, Endophyte, Epichloe festuca, Nickel, Reygrass 55 63 http://jispp.iut.ac.ir/browse.php?a_code=A-10-57-11&slc_lang=en&sid=1 Maryam Salehi Maryam Salehi No Department of Plant Sciences, Faculty of Sciences, Shahrekord University, Iran Department of Plant Sciences, Faculty of Sciences, Shahrekord University, Iran Leila shabani Leila shabani lshabani@gmail.com Yes 1Department of Plant Sciences, Faculty of Sciences, Shahrekord University, Iran 2Research Institute of Biotechnology, Shahrekord University, Shahrekord, Iran 1Department of Plant Sciences, Faculty of Sciences, Shahrekord University, Iran 2Research Institute of Biotechnology, Shahrekord University, Shahrekord, Iran Mohammad reza Sabzalian mohammad reza Sabzalian No Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111 Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111