. ▁It ▁is ▁observed ▁that ▁free ▁living ▁fung i ▁ordin arily ▁have ▁very ▁slight ▁losses ▁of ▁Pi , ▁thought ▁to ▁be ▁due ▁to ▁the ▁re - abs or pt ive ▁nature ▁of ▁the ▁fung al ▁hy pha e , ▁but ▁it ▁is ▁proposed ▁that ▁during ▁sym b ios is ▁the ▁re abs or ption ▁of ▁Pi ▁is ▁reduced ▁thus ▁increasing ▁the ▁net ▁eff l ux ▁out ▁of ▁the ▁fung i . ▁Both ▁path ways ▁depend ▁on ▁relatively ▁high ▁concentr ations ▁of ▁Pi ▁in ▁the ▁fung al ▁cells ▁and ▁low ▁Pi ▁concentr ations ▁inside ▁the ▁plant ▁cell ▁for ▁efficient ▁transport , ▁although ▁the ▁second ▁method ▁is ▁far ▁more ▁dependent ▁on ▁this ▁condition . ▁Additionally ▁these ▁methods ▁are ▁not ▁mut ually ▁exclusive ▁and ▁may ▁occur ▁in ▁the ▁same ▁individuals , ▁but ▁more ▁research ▁is ▁required ▁to ▁un cover ▁the ▁complex ities ▁of ▁the ▁interaction . ▁To ▁facil itate ▁ph osph orus ▁exchange ▁an ▁array ▁of ▁gen es ▁are ▁up reg ulated ; ▁Pi ▁trans porter ▁gen es ▁such ▁as ▁M t PT 4 ▁and ▁St PT 3 ▁are ▁up ▁reg ulated ▁in ▁orch ids ▁plants ▁along ▁with ▁H + ▁ATP ase ▁trans por ters . ▁F ung al ▁partners ▁up reg ulated ▁Pi ▁trans porter ▁gen es ▁as ▁well ▁as ▁al kal ine ▁ph osph at ase ▁encoding ▁gen es ▁( Per otto ). ▁The ▁up reg ulation ▁of ▁ph osph at ase ▁gen es ▁is ▁significant ▁in ▁that ▁it ▁indicates ▁that ▁a ▁significant ▁portion ▁of ▁the ▁ph osph orus ▁obtained ▁by ▁the ▁fung i