phytoremediation, we conducted a literature survey and correlated HM uptake and relative plant

14 To estimate dynamics of arbuscular mycorrhizal (AM) symbiosis in heavy metal (HM) 15 phytoremediation, we conducted a literature survey and correlated HM uptake and relative plant 16 growth parameters from published data. After estimating AM feedback responses for these 17 parameters at low and high soil-HM concentration intervals, we determined that the roles of AM 18 symbiosis are characterized by (1) an increased HM phytoextraction via mycorrhizospheric 19 ‘Enhanced Uptake’ at low soil-HM concentrations, and (2) a reduced HM bioavailability via AM 20 fungal ‘Metal-Binding’ processes at high soil-HM levels, hence resulting in increased plant 21 biomass and enhanced plant tolerance through HM stress-avoidance. We present two conceptual 22 models which illustrate the important compromise between plant growth, plant HM uptake and 23 HM tolerance, and further emphasize the importance of AM symbiosis in buffering the soil 24 environment for plants under such stress conditions. 25 “Capsule”: This meta-analysis has revealed a transition role of the AM symbiosis in 26 phytoremediation shifting from ‘Enhanced Uptake’ to ‘Metal-Binding’ beyond critical soil-HM 27 levels. 28