Analysis of plant/fungi interactions in the presence of mercury

Background/Question/Methods As a result of industrial activities many soils are contaminated with various heavy metals. This study examined plant/mycorrhizal fungi interactions in the presence of heavy metal contaminates. Adaptation of trees to soil environments contaminated with heavy metals are mainly due to phenotypic plasticity and/or microbial community connections. Trees and microbial communities established in contaminated sites may help to protract heavy metals from entering the foodweb by chelation, accumulation, and/or translocation within specialized compartments. In the 1950s and 1960s a large amount of mercury was discharged into East Fork Poplar Creek (EFPC) from the U.S. Department of Energy's Oak Ridge Site, in Oak Ridge, Tennessee U.SA. Presently several tree species inhabit the floodplain of the EFPC, in particular the American sycamore (Platanus occidentalis) which prefer to grow along stream banks and in low lying areas. Sycamore seeds were grown in sterile soil inoculated with soil cores from established plots along EPFC to allow fungal colonization. Seedlings were analyzed for “mercury tolerance” by watering them with 100 ppm of mercuric nitrate, mercuric chloride or a combination of the two for one month. Total mercury in the roots and leaves were analyzed by Cold Vapor Atomic Absorption. The percentage of root mycorrhizal colonization was assessed following staining with trypan blue.  Infrared spectroscopy was utilized to detect chemical changes within the leaves of the sycamore seedlings.
Results/Conclusions Total mercury in roots ranged from 4.9 to 3266 mg Hg/ kg, whereas in leaves total mercury ranged from 1.0 to 242.9 mg Hg/ kg.  Within roots, inoculation (α = 0.02) and mercury treatment (α = 0.001) were significant. The interaction resulted in no significant ( α = 0.07). Various authors have suggested that fungal/plant interaction are a added benefit in the presence of heavy metal contaminates.