symbiosis

[Lewis Melville]

Peter Herman x5495 (rpeter at nmsu.edu) 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