Glomus intraradices Enhances Growth and Gas Exchange of Lolium perenne Seedlings in Petroleum-contaminated Soil

Abstract

Arbuscular mycorhizal fungi (AMF) have been used in phytoremediation and can increase tolerance and growth of plants in contaminated environments. However, little is known about the influence AMF on plant growth to organic contaminants in soils. A greenhouse experiment was conducted to study the response of seedlings of annual ryegrass (Lolium perenne L.) var. Passerel Plus inoculated with Glomus intraradices Schenck & Smith in soil contaminated with sweet Arabian median crude oil. Inoculated (AMF) and non-inoculated (Non-AMF) plants were established in an pasteurized and artificially contaminated sandy loam soil with 0; 3000; 15,000; or 45,000 mg of petroleum kg-1 soil (n = 20). Plants were inoculated with 500 spores of G. intraradices (Mycorise® ASP, PremierTech Biotechnologies, Canada). After 90 days, plant growth of AMF or Non-AMF plants, was drastically affected at all petroleum concentrations. However, G. intraradices enhanced plant growth, chlorophyll content, and gas exchange of plants grown at 3,000 mg kg-1 compared to Non-AMF plants. Total leaf area, chlorophyll, and net photosynthesis were also higher (+380%, +63%, and +81%, respectively) at this concentration. Water use efficiency (net photosynthesis/stomatal conductance) of AMF-plants was three times greater than Non-AMF at 3,000 mg·kg-1. At concentrations of 15,000 and 45,000 mg kg-1 AMF did not have effect, but colonization was observed (11.8% and 18.6%, respectively). These values of colonization were significantly lower than those observed in AMF-plants at 0 (42.5%) and 3,000 mg·kg-1 (55.6%). Studies are currently being conducted to understand the physiological role of AMF on plants exposed to organic contaminants.