© 1993 Heron Publishing—Victoria, Canada
Effect of ammonium on glutamine synthetase activity in ectomycorrhizal fungi, and in mycorrhizal and non-mycorrhizal Scots
pine seedlings
Tytti Sarjala
The Finnish Forest Research Institute, Parkano Research Station, SF-39700 Parkano, Finland / Received December 3, 1991
Summary
The influence of ammonium on glutamine synthetase activity (GS, EC 6.3.1.2) was studied in three species of ectomycorrhizal
fungi, Paxillus involutus (Batsch:Fr) Fr, Piloderma croceum Erikss. and Hjortst. and Suillus variegatus (Fr) O Kuntze growing in pure culture, as well as in the roots and needles of nursery-grown, non-mycorrhizal and mycorrhizal
Scots pine (Pinus sylvestris L.) seedlings inoculated with Paxillus involutus or Piloderma croceum as the symbiont. In response to increasing concentrations of ammonium in the nutrient solution, GS activity (expressed on
a dry weight basis) increased slightly in Suillus variegatus but not in the other fungi. Glutamine synthetase activity increased in the roots and decreased in the needles of non-mycorrhizal
seedlings as the ammonium concentration in the nutrient solution was increased from 0 to 1 mM, but no response was noted with
further increases from 1 to 12 mM. Interspecies differences in GS activity were noted among the fungi growing in pure culture,
but no significant interspecies differences were observed among the same fungi in the mycorrhizal state.
Keywords:
mycorrhizae, nitrate, nitrogen assimilation, Paxillus involutus, Piloderma croceum, Pinus sylvestris, Suillus variegatus, free-living fungi.
