deletions | additions       diff --git a/Fungal_weathering_in_the_lab__.md b/Fungal_weathering_in_the_lab__.md  index 083dd48..04c0a57 100644  --- a/Fungal_weathering_in_the_lab__.md  +++ b/Fungal_weathering_in_the_lab__.md 
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One problem with axenic solution experiments is that no sink (the plant) is available for the released elements. In one study with axenic pine seedlings ectomycorrhizal with *P. involutus*, \citet{Bonneville_2011} found large removal of K, Mg and Fe under hyphae attached to biotite, which suggests that hyphal attachment, and a sink for element removal (the plant) is important for mineral dissolution to occur.   Furthermore, it could be demonstrated that the biotite surface was strongly acidified under the hyphae, which suggests that specific chemical conditions occur under biolayers formed by the fungal mycelium.  \citet{Schmalenberger_2015} demonstrated mineral specific exudation of oxalate by *P. involutus* using labelled 14CO2 ¹⁴CO₂  given to the host plant. Oxalate was exuded in response to minerals in the following sequence Gabbro > limestone, olivine and basalt > granite and quartz.  Active weathering by EMF presumes that elements provided by the minerals are in short supply, and that fungal weathering activity will increase if these nutrients become growth limiting.