plants parasitic on fungi

Jack Murphy jmurphy at FMNH785.FMNH.ORG
Thu Mar 21 10:24:49 EST 1996

Dear myconetters;
        One of the most interesting cases of plant parasitism on fungi
involves orchids.  I'm not well informed on the matter, but I seem to recall
that some orchids parasitize mycorrhizal fungi.  Someone please correct me
if necessary, but I think that the deal is as follows:  the orchid allows
the mycorrhizal fungus to "infect" it, the fungal hyphae penetrate the root
cells of the orchid, and then the orchid turns the tables on the mycorrhizal
fungus and digests it, and that's how the orchid gets its nutrition.  I
don't think the mycorrhizal fungus benefits from this relationship.  How the
orchid attracts the mycorrhizal fungus to begin with is an interesting question.
        This is especially interesting when you consider the flow of
carbohydrates:  they are first synthesized by an un-named plant (the
mycorrhizal fungus's host), they pass to the mycorrhizal fungus in the
normal manner, and then they pass to the "predatory" orchid.  Is the orchid
parasitic on the fungus, or is it parasitic on the fungus' host?  Or both?
        Monotropa is not an orchid (it's in the Mint family, isn't it?); and
does a similar thing.
        In these cases, I doubt that chitin is being digested by the fungi,
but I'm not sure about this.

        Please help me out here if I got these stories wrong -

Dr. John (Jack) Murphy  (JMURPHY at
Dept. of Botany
Field Museum of Natural History
Chicago, IL 60605-2496
(312) 922-9410 ext. 722
fax (312) 427-2530

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