Abstract/Summary

Cadmium (Cd) is one of the most harmful metals in the environment, because even in a low concentration they affect human and other organisms. Cd when in the soil impose severe threats on crop production and food safety. One of the major remediation techniques is phytoremediation, which is a use of plants to immobilise or extract heavy metal from the soil. This thesis studies the effect of Cadmium (Cd) in the mycorrhizal system and in saprotrophic fungi. The main hypothesis tested was common mycorrhizal network increases the amount of cadmium extracted from the soil and the cadmium uptake dynamics. In order to understand that system, ectomycorrhizal fungi were tested under Cd along with its effect on carbon cycling enzymes. The experiments conducted in this project aimed to investigate the potential of poplars trees (Populus trichocarpa), colonised by the arbuscular mycorrhizal fungus Rhizophagus irregularis, to improve metal uptake in the host plant as well as in combination with different species under contaminated soil with Cd. Additional aims were to investigate common mycorrhizal networks and their potential to transfer Cd between plants, and to understand the physiological processes by which Cd can affect ectomycorrhizal and saprotrophic fungi. Results showed that mycorrhizal P. trichocarpa have increased Cd accumulation in their roots, which supports their use for Cd phytoextraction. Experiments with common mycorrhizal networks showed that Cd can be transported between P. trichocarpa trees. This result opens many other opportunities for exploring this complex system and the likely importance of having neighbouring plants to establish new vegetation in contaminated soil. Cd contamination increased the production of GSRP (glomalin) in all arbuscular mycorrhizal plants, but mostly in leeks. Glomalin as known as soil glycoprotein, which apart from being responsible for stabilization of soil aggregation also act as a soil protector by binding the metal under Cd contamination. It was also found that Cd can affect mycorrhizal and soil microorganism producing of carbon enzymes, however there was a wide variation within different species. Cd was able to reduce soil enzyme activity of xylanase by 50%, demonstrating how Cd can affect contaminated areas and its dynamics. Some species of saprotrophic fungi showed a potential to be used for Cd remediation, but there are a wide range of species to be explored in this field. This thesis offers new opportunities to explore properties of common mycorrhizal networks and to enhance our knowledge on Cd contamination. The knowledge gathered in this project may help further research in Cd remediation technique.