Plant nutrients, with the exception of nitrogen, are ultimately derived fro
m weathering of primary minerals. Traditional theories about the role of ec
to mycorrhizal fungi in plant nutrition have emphasized quantitative effect
s on uptake and transport of dissolved nutrients. Qualitative effects of th
e symbiosis on the ability of plants to access organic nitrogen and phospho
rus sources have also become increasingly apparent, Recent research suggest
s that ectomycorrhizal fungi mobilize other essential plant nutrients direc
tly from minerals through excretion of organic acids. This enables ectomyco
rrhizal plants to utilize essential nutrients fro m insoluble mineral sourc
es a nd affects nutrient cycling in forest systems.