'Not all that tempts the listless hearts and wandering eyes is lawful prize.
Nor all that glistens gold' - Gray
I got the following E-mail last week:
"I went on a hike from Dwight to Maggie Lake (Ontario) and saw two growths of fungi I haven't been able to identify. Thin, translucent white stalks about 3 inches tall in groups of 2-3 with delicate knodding heads of the same material edged with delicate grey-soft black. Wasn't in the Audubon book, your website or any other. Thought you might be interested."
Strange looking, ghostly white things growing in woods are not always fungi. The E-mail describes Monotropa uniflora known as 'Indian Pipe' or 'Ghost Plant' and it also has other common names. The image below is the top half of Monotropa. If you want to see the whole plant click here.
When I was writing my book on mushrooms I included a few other things such as corn smut, powdery mildews, a few insect parasites and the like and I almost included Monotropa. I didn't for two reasons as 1) it is not a fungus but is a higher plant related to heather (Ericaceae) and 2) I thought everybody would already know it. But maybe not, eh! At any rate, I checked the web and there is a lot of good info on Monotropa but unfortunately more sites have the biology wrong than have it right and all in all it's a bit confusing. Some say it is a saprophyte on dead organic stuff; others that it is parasitic on tree roots; a few were very vague about the whole thing; and one or two got it right. So this month I'm going to give a brief explanation of the biology of Monotropa.
Monotropa is a non-chlorophyllose higher plant that has lost its independent photosynthetic way of life and now lives as a parasite.
Background: IF YOU ARE FAMILIAR WITH MYCORRHIZAE MOVE ON TO NEXT PARAGRAPH ! Forest trees are not independent organisms but survive in a mutually advantageous relationship as partners with fungi in their roots. These mycorrhizae (fungus roots) are essential to the survival of both the tree and the fungus. The tree gives to the fungus the carbohydrates that it synthesises in its leaves. In return, the fungus supplies the tree with water and nutrients (N, P, K etc.) absorbed by its hyphal system in the forest soils. This is a truly mutualistic symbiotic association. Frpm their main root system conifers form short, branching, stubby side roots called coralloid roots. The fungus forms a sheath around these roots and the fungus filaments (hyphae) grow out (unlimited growth) from this locus to exploit the surrounding area far better than the root hairs of the pine that have a limited growth i.e relatively very short and of fixed length. In other words do a better job for the tree than its own root hairs. Because it forms an external sheath around the roots this association is often referred to as ectomycorrhizae. Some plants have an internal mycorrhizal association called endomycorrhizae but that is for another day.
Summary of the Monotropa story.
In the mycorrhizal association between the tree and the fungus, the tree supplies the ectomycorrhizal fungus with carbohydrates from the photosynthetic factory in the leaves. In return the mycorrhizal fungus supplies the tree with water and nutrients (NPK etc.) for its growth and development. Monotropa taps into this system through the fungus component and sets up its own mycorrhizal association with the fungus partner of the tree. Probably this is accomplished by hormonal systems by which Monotropa sets itself up as a nutrient sink and diverts water and mineral nutrients directly from the fungal hyphae. At the same time it filches off some carbohydrates (sugars) that the fungus has obtained from the tree. As far as we know, Monotropa gives nothing to either the fungus or the tree. Thus, Monotropa is directly parasitic on the fungus for water and minerals and indirectly parasitic on the tree for sugars using the fungus as a conduit. To see diagram of this click here.
1. If you dig up the Monotropa you will find (as you might expect) that it has short, stubby, coralloid roots i.e supplied with a fungal sheath (ectomycorrhizal).
2. No chlorophyll! No photosynthesis! So, it doesn't need light and can grow in the darkest forest.
3. Must have potent hormonal systems to develop a nutrient 'sink' and direct (steal) the sugars away from the fungus for its own development.
4. Note the interesting modifications. Doesn't photosynthesise so is morphologically very reduced. i.e. no branches and the leaves are reduced to membranous scales (i.e. vestigial). All in all a neat evolutionary adaptation to the easy life. Scale leaves have no legitimate function and should eventually disappear (might take million years or so).
1. Think how all of this might have begun!
2. Do you think it likely that other plants, even photosynthetic plants, could tap into a mycorrhizal system!
3. From question 2. Do you think a mycorrhizal tree could 'breast feed' its own seedlings or those of other mycorrhizal trees? What advantage would this have for a tree seedling?
4. Using steel plates and radioactive chemicals or other methods how would you show that the Monotropa is dependent on the tree/ fungus system? (It's been done. Check the web).
5. The association between Monotropa and the fungus is symbiotic but is not mutualisitic. Define the term 'symbiosis'. Many people who should know better get the definition wrong! What term would you use to define the relationship between Monotropa and the fungus? (two words!)
6. How many other plants do you know that have evolved to this way of life? i.e. no chlorophyll and dependent on fungi or another plant for their parasitic existence. Check out You will find quite a few but, in case you miss it, check out Cryptothallus mirabilis. This was originally described as a saprophytic liverwort. What would you think now?
7. Have you ever heard of Psilophyton?