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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