What reasons do you have for thinking that mycorrhizas may influence P-(de)sorption which is meant to be purely exchange of PO4--P in the absence of microbial activity?
The following paper provides comprehensive information on inorganic Pi uptake , transport and storage as polyphosphate in plant. As I understand only two forms of are involved i.e., soluble orthophosphate (Pi) and polyphosphate.
Fungal association and utilization of phosphate by plants:success, limitations and future prospects. Frontiers in Microbiology October 2015