Ministry of Forests

Cariboo Region Research Section

Haemoglobin in Tuberculate Ectomycorrhizae on Lodgepole Pine - Abstract submitted to ICOM 2 July, 1998 Upsula Sweden

Haemoglobin has been found within the tissue of tuberculate ectomycorrhizae (TEM) on lodgepole pine (Pinus contorta  var. latifolia Engelm. ex S. Wats.).  Acetylene reduction assays demonstrated that nitrogen fixation occurs in lodgepole pine TEM, and N2 -fixing bacteria have been isolate from within the tubercules.  A pinkish cast to many of the TEM was reminiscent of nitrogen fixing nodules and caused us to look for haemoglobin (in spite of the fact that some of the fungi involved in forming these mycorrhizae are known to stain pink).  Initially, the Drabkin’s Reagent test was used to determine the presence of haemoglobin in homogenized TEM tissue,  Samples weighing 0.5 g resulted in a range of total haemoglobin concentrations from 5.6 - 9.7 mg/dl (n=15).  To confirm the Drabkin’s Reagent tests, gel electrophoresis techniques were also used.  All tests were positive in both protein and haemoglobin stains when compared to a human haemoglobin standard solution of 1 mg/ml.  This study is the first to report the occurrence of a haemoglobin associated with TEM or a tripartite structure (fungus/plant/bacteria) of this type.  Since this study found nitrogen fixing bacteria within tubercles and since these bacteria fix nitrogen optimally under microaerophillic conditions, the presence of haemoglobin within the tubercle suggests that TEM are formed to regulate the amount of oxygen being supplied to symbiotic N2-fixing bacteria and are a structure analogous to legume or Frankia nodules.

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