Subject: Re: symbiosis

From: Thomas O'Dell <[email-masked]>
Date: Mon, 24 Oct 1994 09:11:31 -0700

legumes (especially sub genera Papillionoideae and Mimosoideaea) tend to 
be highly va mycorrhiza dependant. the plant-fungal-bacterial symbiosis 
is commly referred to as tripartite and has been the subject of 
considerable research. certainly hundreds of papers exist on the topic 
particularly re soybean, clover and other ag. crop plants. 
actinorrhizal (frankia-nodulated) plants also tend to be mycorrhizal, va 
or ecto (e.g. alnus; dryas) depending on the plant species.

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From: [email-masked]
Date: 24 Oct 1994 06:52:09 -0700

I had a student ask an interesting question this AM.  "Are there any plants
that form mutualistic relationships with both bacteria and fungi at the same
time?"  I told her that I couldn't give her a specific example but I didn't
see why it couldn't happen. Does anyone know of examples of this?  Do legumes
containing Rhizobium also show endo or ecto mycorrhizal associations?

Dave

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From: [email-masked] (Lewis Melville)
Date: 26 Oct 1994 17:56:06 GMT

Peter Herman x5495 ([email-masked]) wrote:
: >I had a student ask an interesting question this AM.  "Are there any plants
: >that form mutualistic relationships with both bacteria and fungi at the same
: >time?"  

	Alnus sp. ( alder ) forms an association with Frankia ( an 
actinomycete ) and Alpova sp. ectomycorrhizal fungi. Dryas sp. forms an 
association with Frankia and many types of ectomycorrhizal fungi, such as 
Hebeloma sp., Cenococcum sp., Laccaria sp.. Both Alnus and Dryas occur in 
northern and Boreal forest, often in nutrient depleted zones or recently 
glaciated regions. It appears as though they need the extra help to 
establish themselves in difficult growing areas. The Frankia provides a 
Nitrogen boost, and the fungi colonize the roots for sugars produced by 
the plant and fungal hyphae grow out into the soil and acquire Phosphorus 
and other minerals which are not accessible to the plant. Or so the 
theory goes... 
There are also nitrogen fixing bacteria found in association with several 
ectomycorrhizal fungi in the mantle which surrounds the plant roots. 
The root, bacteria, and fungi, also interact with other soil organisms 
such as nematodes, all the way across the chain to small mammals which 
dig up truffles of hypogeous mycorrhizal fungi, eat them, and then 
disperse the spores of the fungi in their excrement, etc, etc,.... 
Soil microenvironments are very complex........
lewis melville

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From: Vikram Prabhu <[email-masked]>
Date: Wed, 26 Oct 1994 10:35:30 -0600

Plants that have N fixing bacteria such as soybean form VA mycorrhizae, 
and others like Alnus form ectendo and ectomycorrhizae (perhaps VA too) and 
there are several good studies demonstrating that N fixation increases the 
phosphate demand (thru increased growth) which is supplied by the fungus (or 
vice versa; chicken or egg argument).

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From: [email-masked] (Peter Herman x5495)
Date: 25 Oct 1994 07:10:10 GMT

>containing Rhizobium also show endo or ecto mycorrhizal associations?

You are correct in your assumption that legumes can be nodulated by
rhizobia and be mycorrhizal as well.  I know for sure it occurs in
Pisum, Trifolium and Medacago having read papers on all these with
nodules and VAM.  I don't know for sure if Alnus or Myrica and the
other streptomycete symbionts but I would be surprised if it is not
the case

Peter Herman
Biology
New Mexico State Univ.