02218naa a2200265 a 450000100080000000500110000800800410001910000250006024501470008526000090023252014730024165000110171465000150172565000090174065000120174965000130176165000090177465300270178365300110181065300150182165300250183665300290186170000180189077300440190815527041997-04-15       1994    bl ---       0--  u    #d1 aMIRANDA, J. C. C. de  aThe effect of soil phosphorus on the external mycelium growth of arbuscular mycorrhizal fungi during the early stages of mycorrhiza formation.  c1994  aThe effects of soil P amendments and time of application on the formation of external mycelium by different arbuscular mycorrhizal (AM) fungi were studied. In the first experiment the external mycelium produced in the soil by the AM fungus Glomus etunicatum Beck. and Gerd., during the early stages of root colonization (7 and 14 days after inoculation), was quantified by the soil-agar film technique. A Brazilian Oxisol was used with three different phosphate and inoculation treatments for plant dry weight, P content in the tissue, root length and root colonization, at fourteen days after planting. At 7 days, mycelium growth, root colonization and their relationship were reduced at supra-optimal P concentrations. Applications of P one week after planting reduced mycelium growth and root colonization more than when applied to the soil before planting. In a second experiment the arbuscular mycorrhizal (AM) fungi, Scutellospora heterogama (Nicol. and Gerd.). Walker and Sanders and E3 were tested and compared with Glomus etunicatum. For the species studied, the length of external hyphae per unit of colonized root length was affected by small P additions but no further significant differences were observed at high P levels. The three AM endophytes showed marked differences in their response to P in the soil: Scutellospora heterogama, although producing external mycelium more profusely than the Glomus spp., showed a higher sensitility to soil P supply.  aBrazil  aphosphorus  asoil  aCerrado  aFósforo  aSolo  aArbuscular mycorrhizae  aBrasil  aGlomus spp  aMicorriza arbuscular  aScutellospora heterogama1 aHARRIS, P. J.  tPlant and Soilgv.166, p.271-280, 1994.