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Keywords:

  • Ectomycorrhizas;
  • aluminium;
  • phosphorus;
  • Pinus rigida;
  • Pisolithus tinctorius

SUMMARY

Mycorrhizal infection of roots of Pinus rigida Mill, seedlings by Pisolithus tinctorius Coker & Couch maintained normal foliar P relations when seedlings were exposed to Al in solution. To investigate how this symbiosis aids in P acquisition in the presence of Al, seedlings were grown in sand culture with solutions containing between 1 and 50 μM NaH2PO4 (Pi) with or without insoluble AlPO4 in the substrate. Mycorrhizal seedlings had a higher affinity for Pi than non-mycorrhizal seedlings as judged by superior growth and foliar P contents at all Pi levels tested. In addition, mycorrhizal seedlings, but not nonmycorrhizal seedlings, effectively extracted P from AlPO4 through the dissolution of this insoluble salt. Measurement of matrix solution pH indicated that increased proton production, in association with high proliferation of mycorrhizal roots under P-limiting conditions, led to increased AlPO4 solubilization.