This month's fungus is not a fungus at all, but is often brought in to forays and by students thinking it must be a fungus because it's white and doesn't have any chlorophyll. But it's really a flowering plant-- in the blueberry family! This is one of about 3000 species of non-photosynthetic (i.e. heterotrophic) flowering plants. How does this plant survive?? I'll tell you later of the interesting way that this non-photosynthetic plant gets its food. Monotropa uniflora can actually grow in dark (and spoooooooooky) environments because it is not dependent on light for photosynthesis. I tend to find this plant in rich habitats-- dense moist forests with much surface leaf litter, often in a situation that is too shaded for autotrophic (photosynthetic) growth. Finding the ghost plant is an indication to me that I am in a very rich woods, and I should be on the lookout for lots of interesting fungi. Monotropa uniflora is the most common species in Wisconsin and the rest of North America east of the Great Plains. It is also known from Japan, and probably occurs in other places as well. There are relatives of this plant that occur throughout the world. There are at least 3000 species of non-photosynthetic members of the plant kingdom. All of these are vascular flowering plants (angiosperms), except for one weird non-photosynthetic liverwort that I know of (Cryptothallus mirabilis). Many of these angiosperms are members of the Ericaceae, a family that also includes blueberries, cranberries, heath, Rhododendron, azaleas, Arctostaphylos, and Arbutus. There are many other species of Monotropa, as well as other genera of mycoparasitic plants including Pterospora, Hermitomes, Sarcodes, Pityopus and others. All of these non-photosynthetic members of the Ericaceae belong to the subfamily Monotropoideae. There are a number of other plants in other families that I will discuss later. Since all of these plants are heterotrophic, they must get their food from an outside source. Almost all are parasitic on other organisms. Many (like mistletoe and dwarf mistletoe) are directly parasitic on other plants. However, most of these heterotrophic plants, and certainly all of the monotropes are parasitic on fungi! These fungi are mycorrhizal with photosynthetic trees, and thus the energy ultimately comes from photosynthesis of the tree, passing through the mycorrhizal fungus on the way to the Monotropa. The tree, already providing energy to the fungus, is probably physiologically 'unaware' of the additional loss of carbon and it is likely that it is the fungus that controls the passage of carbon to Monotropa. The one-way flow of carbohydrates can be traced by supplying the photosynthetic tree with radioactive carbon dioxide, i.e. 14CO2. In the animated diagram to the left, green represents the shoot of the photosynthetic plant, brown is the roots of the photosynthetic plant, light blue is the mycorrhizal fungus, dark blue is the Monotropa, the large blue circle is a plastic bag put over a leaf to provide an environment to release the radioactive carbon dioxide, and the small circles represent various forms of radioactive carbon molecules. Inside the bag, the radioactive carbon dioxide is photosynthesized into radioactive sucrose, which is transported to the roots of the tree. The mycorrhizal fungus takes the radioactive sucrose and transforms it into radioactive trehalose or sugar alcohols, which are transported to the rest of the fungal mycelium. (In return the fungus aids the tree in absorption of water and essential minerals, especially phosphorous, but that's a whole 'nother story...) The Monotropa absorbs the sugars from the fungus by "fooling" the fungus into thinking it's forming a mycorrhizal relationship-- but in fact the Monotropa is really parasitizing the fungus!. Thus the radiolabeled carbohydrates pass from the tree to Monotropa via their common mycorrhizal partner, in what is termed a source-sink relationship. In other words, the sugars flow from where they are made to where they are being used. Thus this is a three-way relationship between a photosynthetic tree, a mycorrhizal fungus, and a parasitic plant! You can see why some other terms for these monotropes that benefit from this ménage á trois are myco-heterotrophic plants, mycoparasitic plants, or epiparasitic plants The fungi involved are very diverse. According to Martín Bidartondo, who has done some excellent work in Tom Bruns' lab at the University of California at Berkeley, Monotropa uniflora forms a relationship with Russula and Lactarius species. Monotropa hypopithys forms a relationship with various Tricholoma species. Sarcodes sanguinea (pictured below) forms a relationship with various Rhizopogon species. You can click here for Bidartondo and Bruns, 2001. "Extreme specificity in epiparasitic Monotropoideae (Ericaceae): widespread phylogenetic and geographical structure." This paper is very interesting and has a list of the species involved in all the relationships, along with triple phylogenies of all the symbionts. Very well done! As I mentioned previously there are a number of other plants that are mycoheterotophic. Some, like the snow plant (A. Sarcodes sanguinea), found in the Sierra Nevada mountains of California, are monotropes, related to Monotropa. B is broomrape, from the mountains of northern New Mexico. C is Monotropa hypopithys>, a multicolored monotrope (picture from Oregon, I think.) D is squaw root, Conopholis americana, apparently directly parasitic on roots. You can email me if you recognize any of the plants I haven't named. There are a number of other species of heterotrophic plants not pictured, such as Pine drops, beech drops, and many others. They're very widespread, and I bet you can find some near where you live. Myco-heterotrophism in plants is more widespread than we first thought. Bidartondo et al. have recently (2002, 419: 389-392 ) published a Nature paper "Epiparasitic plants specialized on arbuscular mycorrhizal fungi" showing that some arbuscular mycorrhizal fungi (from the Zygomycota, or if your prefer the new classification for AMF, the Glomeromycota) can also participate in this three-way association. This significantly increases the range of organisms that can participate. Things underground just keep getting more complicated. Click here to read the article online. I hope you enjoyed learning something about Monotropa uniflora and its associates today. There's A LOT going on underground that we're just starting to understand. Please leave these beautiful plants in the woods where they have some important function in the ecosystem. They're very beautiful for you and later visitors to find. If you have recommendations for future FOTM's please write to me at volk.thom@uwlax.edu If you have anything to add, or if you have corrections or comments, please write to me at volk.thom@uwlax.edu This page and other pages are © Copyright 2002 by Thomas J. Volk, University of Wisconsin-La Crosse. Return to Tom Volk's Fungi Home Page --TomVolkFungi.net
This month's fungus is not a fungus at all, but is often brought in to forays and by students thinking it must be a fungus because it's white and doesn't have any chlorophyll. But it's really a flowering plant-- in the blueberry family! This is one of about 3000 species of non-photosynthetic (i.e. heterotrophic) flowering plants. How does this plant survive?? I'll tell you later of the interesting way that this non-photosynthetic plant gets its food.
Monotropa uniflora can actually grow in dark (and spoooooooooky) environments because it is not dependent on light for photosynthesis. I tend to find this plant in rich habitats-- dense moist forests with much surface leaf litter, often in a situation that is too shaded for autotrophic (photosynthetic) growth. Finding the ghost plant is an indication to me that I am in a very rich woods, and I should be on the lookout for lots of interesting fungi. Monotropa uniflora is the most common species in Wisconsin and the rest of North America east of the Great Plains. It is also known from Japan, and probably occurs in other places as well. There are relatives of this plant that occur throughout the world.
There are at least 3000 species of non-photosynthetic members of the plant kingdom. All of these are vascular flowering plants (angiosperms), except for one weird non-photosynthetic liverwort that I know of (Cryptothallus mirabilis). Many of these angiosperms are members of the Ericaceae, a family that also includes blueberries, cranberries, heath, Rhododendron, azaleas, Arctostaphylos, and Arbutus. There are many other species of Monotropa, as well as other genera of mycoparasitic plants including Pterospora, Hermitomes, Sarcodes, Pityopus and others. All of these non-photosynthetic members of the Ericaceae belong to the subfamily Monotropoideae. There are a number of other plants in other families that I will discuss later.
Since all of these plants are heterotrophic, they must get their food from an outside source. Almost all are parasitic on other organisms. Many (like mistletoe and dwarf mistletoe) are directly parasitic on other plants. However, most of these heterotrophic plants, and certainly all of the monotropes are parasitic on fungi! These fungi are mycorrhizal with photosynthetic trees, and thus the energy ultimately comes from photosynthesis of the tree, passing through the mycorrhizal fungus on the way to the Monotropa.
The tree, already providing energy to the fungus, is probably physiologically 'unaware' of the additional loss of carbon and it is likely that it is the fungus that controls the passage of carbon to Monotropa. The one-way flow of carbohydrates can be traced by supplying the photosynthetic tree with radioactive carbon dioxide, i.e. 14CO2.
In the animated diagram to the left, green represents the shoot of the photosynthetic plant, brown is the roots of the photosynthetic plant, light blue is the mycorrhizal fungus, dark blue is the Monotropa, the large blue circle is a plastic bag put over a leaf to provide an environment to release the radioactive carbon dioxide, and the small circles represent various forms of radioactive carbon molecules.
Inside the bag, the radioactive carbon dioxide is photosynthesized into radioactive sucrose, which is transported to the roots of the tree. The mycorrhizal fungus takes the radioactive sucrose and transforms it into radioactive trehalose or sugar alcohols, which are transported to the rest of the fungal mycelium. (In return the fungus aids the tree in absorption of water and essential minerals, especially phosphorous, but that's a whole 'nother story...) The Monotropa absorbs the sugars from the fungus by "fooling" the fungus into thinking it's forming a mycorrhizal relationship-- but in fact the Monotropa is really parasitizing the fungus!. Thus the radiolabeled carbohydrates pass from the tree to Monotropa via their common mycorrhizal partner, in what is termed a source-sink relationship. In other words, the sugars flow from where they are made to where they are being used. Thus this is a three-way relationship between a photosynthetic tree, a mycorrhizal fungus, and a parasitic plant! You can see why some other terms for these monotropes that benefit from this ménage á trois are myco-heterotrophic plants, mycoparasitic plants, or epiparasitic plants
If you have recommendations for future FOTM's please write to me at volk.thom@uwlax.edu
Return to Tom Volk's Fungi Home Page --TomVolkFungi.net
