ous ▁organ ic ▁comp ounds ▁may ▁be ▁present ▁in ▁the ▁surrounding ▁soil . ▁If ▁so ▁organ ic ▁nit ro gen ▁u pt ake ▁also ▁takes ▁place ▁through ▁am ino ▁acid ▁per me ases ▁and ▁pe pt ide ▁trans por ters . ▁Once ▁incorpor ated ▁into ▁the ▁fung i ▁as ▁am ino ▁ac ids , ▁there ▁are ▁a ▁few ▁different ▁proposed ▁mechan isms ▁with ▁which ▁the ▁nit ro gen ▁is ▁transferred ▁to ▁the ▁host ▁plant . ▁These ▁path ways ▁of ▁nit ro gen ▁transfer ▁are ▁thought ▁to ▁be ▁exclus ively ▁bi ot roph ic , ▁a ▁significant ▁amount ▁of ▁nit ro gen ▁may ▁also ▁be ▁transferred ▁ne c rot orph ically ▁but ▁through ▁a ▁significantly ▁different ▁process . ▁In ▁the ▁first ▁path way ▁ ▁the ▁am ino ▁ac ids ▁are ▁transferred ▁to ▁the ▁extr ar ad ical ▁my cel ium ▁where ▁the ▁am ino ▁ac ids ▁are ▁broken ▁down ▁by ▁the ▁cat abol ic ▁stage ▁of ▁the ▁u rea ▁cycle . ▁The ▁primary ▁am ino ▁acid ▁synth es ized ▁and ▁int ra - f ung ally ▁transferred ▁is ▁arg in ine , ▁which ▁is ▁cat abol ized ▁into ▁am mon ium . ▁The ▁am mon ium ▁is ▁then ▁sh unted ▁into ▁the ▁inter fa cial ▁space ▁between ▁the ▁pel ot on ▁and ▁the ▁surrounding ▁plant ▁memb rane , and ▁transport ed ▁into ▁the ▁plant ▁cell ▁via ▁am mon ium ▁trans por ters ▁and ▁incorpor ated ▁into ▁the ▁plant . ▁ ▁To ▁accommod ate ▁the ▁transport ▁of ▁nit ro gen ▁via ▁this ▁path way ,