Mycorrhizal responses under elevated CO2 : combining fungal and plant perspectives

The rising level of atmospheric carbon dioxide (CO2) combined with increased nutrient (especially nitrogen) availability are predicted to have substantial impacts on plant growth and the functioning of ecosystems. Soil micro-organisms, especially mycorrhizal fungi that form mutualistic associations with plant roots, are key factors in the functioning of ecosystems. Studies of plant responses are therefore of limited realism, if the mycorrhizal symbiosis is ignored. It is therefore important to understand the diversity, extent and dynamics of the mycelia of mycorrhizal fungi in soils. This thesis focuses on the interactions between mycorrhizal fungi, mycorrhizal plants, elevated CO2, and nutrient availability. In conclusion, it is clear the need for a conceptual separation between a mycocentric and phytocentric view is evident for ectomycorrhizal associations. Extraradical hyphal length can cause mycorrhizal fungal-induced Progressive Nitrogen Limitation (PNL) and generate negative feedback with plant growth under elevated CO2. Increasing N supply potentially relieves mycorrhiza-induced PNL under elevated CO2.