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Monotropa uniflora

This is off topic. Specifically botany and mycology. I thought some readers might find it of interest.

I’m vacationing for the summer up north, it’s been wet and warm, perfect for mushrooms so this morning my daughter and I went walking through some woods and fields looking for mushrooms. I really wanted to get a sack of table mushrooms (Agaricus bisporus; button mushroom; portobello) to cook up. All I found in that regard was one lonely old portobello long past its prime. We found lots of boletes, amanitas, lbm’s (little brown mushrooms), death caps, and one odd thing that was sort of mushroom shaped, lumpy, light violet, but no gills I could discern. Disappointingly, no puffballs.

We did find something fairly rare though that I’d seen once before but didn’t know what it was.

indian pipe

Turns out it was a cluster of these, scientific name Monotropa uniflora, common names “Indian Pipe”, “Corpse Plant”, and “Ghost Plant”. My daughter googled them up when we got back using the search term mushroom flower. They have “flesh” that seems indistinguishable from mushrooms, no chlorophyl whatsoever, but they also have unmistakable leaves, petals, pistils, and stamens so I knew they had to be a plant. These things parasitize a mycorrhizal fungus (a fungus that is symbiotic with plant roots). So their ultimate source of nutrients is a normal green photosynthetic plant but it gets those nutrients second hand by way of a fungus and except for the obvious plant parts you’d swear it itself was a fungus.

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13 Responses to Monotropa uniflora

  1. It’s actually not as off-topic as you would think. The Monotropa have small, scale-like leaves, because leaves are detrimental to plants that don’t carry out photosynthesis and don’t need to synthesize carbohydrates. The leaves are not just detrimental due to energy costs – they also lead to water loss. It would be easy to say that an achlorophyllic plant with mutated leaves obviously suffered a loss of genetic information at some point.

    But the Monotropa have very sophisticated adaptations that allow them to tap into the mycorrhizal structures (hormonal/structural – I don’t think they’ve been characterized molecularly yet). I think you, Dave, have talked in the past about starting with perfect designs that then lose their usefulness. So either this plant was created with entirely useless leaves and photosynthetic machinery, but a functional mycorrhizal tap. I don’t mean useless in the sense of non-functional, at least initially. This plant’s sophisticated root system, while good for how it obtains energy now, is not useful for a photosynthetic plant. So even if Monotropa had functional chlorophyll and leaves, those would be useless, if not detrimental.

    Or it evolved this sophisticated ability to take carbohydrates through a fungal tube from other plants and then lost its useless leaves and chlorophyll.

    What’s your take on why this plant is the way it is?

  2. My take is that monotropa are to flowering plants as monotremes are to mammals. Some odd combination of characters from different phyla that never quite made the big leagues in terms of species diversity or large numbers of individuals.

    I’m a fan of front loading where all or most of the complexity of life has been here a very long time and was simply not expressed until the proper environmental triggers came along.

    I’ve got one sitting here in front of me. The leaves aren’t particularly small, about the same size as the petals on the flower. I’m sure I could go out tomorrow and in ten minutes find some green plant with about the same leaf surface area to plant size ratio as this thing.

    At any rate losing leaves and chlorophyll that aren’t needed anymore is a far easier task for random evolution than making them de novo when the need arises. As far as drawing nutrients from a fungus that doesn’t seem to be much of a challenge for normal plant root system – they’ll absorb nutrients from any source they can touch in my experience.

    At any rate I don’t think these things had flowering plants for ancestors any more than monotremes had mammals for ancestors. I think they’ve been around pretty much just like they are for as long as flowering plants have been around. Just an oddball that branched off from a common ancestor at the same time as flowering plants branched off. I’d really like to put this under a microscope and compare the cell structure side by side with a mushroom and a green plant but unfortunately my microscope wasn’t on the list of things to pack into my truck for summer vacation up north. I’d like to see what the pollen looks like too. If it weren’t for the pistil and stamen I’d have sworn this was a fungus.

    Water loss through the leaves doesn’t seem to be a problem. I’ve had two samples sans roots sitting on the desk next to my computer for 12 hours and they haven’t even wilted. What it has done though is turn black around the thin edges of the leaves and petals. Mushrooms turn color like that while plants don’t.

  3. By the way, if you google “monotropa uniflora” my article here is the fifth hit down from the top. PZ and Abbie might believe we don’t have much weight but google sure indexes us like we do. Of course PZ and Abbie were never ones that let reality interfere much with their opinions. :-)

  4. Well, for the Monotropa, it’s not quite as simple as absorbing the carbohydrates. The fungi that are in symbiosis with the trees don’t want to share that with anything except the other fungi, which normally transport minerals to trees in exchange for the carbohydrates. To get the carbohydrates, the monotropa have to mimic some of the fungi’s own chemical signals (it’s here that I don’t think that the molecular characterization is complete – there’s probably no money in it). Their root system is also more of a ball structure that leads to larger networks of fungal hyphae than you find near tree roots.

    And the thing is, to have this kind of relationship with fungi, there already had to be a symbiotic relationship between fungi and trees. Because all the parasitic Monotropa are achlorophyllous. If they didn’t have to live under tree canopies to steal sugar from fungi (and thus other plants) – they could have the best of both worlds – photosynthesis and parasitism. And trees are a relative newcomer in the flowering plants. (I assume that Monotropa only parasitize trees because other plants are too small to provide sufficient sugar/have an extensive commensal fungal network).

    The molecular data also shows that the Monotropa are relatively new – they are closely related to rhododendrons.

    Also, I don’t know about your specific specimen, but Monotropa tend to have small, scale-like leaves. The stomata that are present in all leaves are not airtight and thus there is some significant water loss even when they’re closed. So that is a liability for the plants.

    This is an aside, and may not be that interesting to everyone:
    I was actually wondering why all the Monotropa are achlorophyllous – the parasitic relationship with the fungi must predate the loss of photosynthesis, or they’d have no energy source. And the thing is, the photosynthetic pathway can break a lot of different ways – it doesn’t have to be in the chlorophyll biosynthesis pathway. And then I realized that as long as chlorophyll is around, it’s going to be pumping solar energy into the cell, which is going to wind up making reactive oxygen species that the plant can’t deal with anymore – it can’t put the energy in new sugars. So it has to get rid of the chlorophyll in order to survive.

  5. 5

    By the way, if you google “monotropa uniflora” my article here is the fifth hit down from the top.

    You are obviously not a “rock” star, but you probably qualify as the fungus among-us.

  6. I spent another half hour this morning reading more about uniflora and found one interesting thing in that the mycorrhizal host cooperates in the parasitic relationship. Uniflora doesn’t tap into the mycorrhiza. The mycorrhiza taps into the uniflora roots as if uniflora was one its photosynthetic partners. This leads me to believe uniflora may indeed have a photosynthetic ancestor once parasitized by the fungus but the plant managed to turn the situation around so that instead of the fungus stealing carbohydrates from the plant the plant steals them from the fungus.

    I suppose as full genome sequencing prices drop unitropa’s sequence will eventually be catalogued and some more definitive answers about it can be obtained through comparative genomics.

  7. zylphs

    I read that many achlorphyllic plants do produce small amounts of chloroplasts. Also it wasn’t so dark where I found these that there were no other small green plants in near proximity but they certainly weren’t in lush growth. I was picking a path through the least amount of ground cover as I was wearing shorts and sandals and didn’t want to get all scratched up through higher growing weeds. I recall there were a fair amount of tall pines where I found it and little grows underneath a pine as (I presume) something in the pine needles inhibits the growth of ground cover under the tree. So it may not have been so much of a lack of light as it was unsuitable soil. Fungi don’t seem to have as much of a problem growing under pine trees, especially amanitas, and I wanted my daughter to see one of the prettier ones with bright orange to bright red caps sprinkled with snow white warts. Didn’t find any of those unfortunately. Just some of the less striking ones with beige tops.

    There are two large old cemetaries (I’d guess 40 acres, one Catholic, one protestant, separated by a deep dry creek channel & railroad tracks) near where we were hunting with lots of different and odd species of trees that people have planted over the centuries in them and when I was a kid those cemetaries were a target rich environment for a wide range of mushrooms and puffballs. Today they’re totally devoid of them. I understand the caretakers now use a grass fertilizer that contains a fungicide. The bastards! The myco-utopia I loved as a child is now a myco-free zone.

  8. Back when I lived and worked in Oregon’s Coast Range I’d find a similar plant, it was an orchid if memory serves. It similarly lacked chlorophyl; don’t remember whether parasitic or whether it lived off rotten wood. It was more pinkish than Monotropa uniflora.

    If such plants are found in divergent families then we have something more like the convergent evolution of wings among insects, reptiles, birds and mammals. Doesn’t the gain in specified complexity involved in these plants (the root system, etc.) suggest something more than the loss of it that we see in blind cave fish?

    Orchids, they say, are a rather recent development in the flora of earth.

  9. The two samples are still on my desktop now about 24 hours old. The stems are turning black from the root upward. The flowers and leaves are still almost perfectly white except at the fringes. I examined the stems a little closer and they’re constructed of many thin layers that peel back easily until you get to a fibrous center region. It reminds me of the root of a leek or wild onion in color, water content, and structure. The odd thing is still the color change. A dried onion doesn’t change color. There must be some chemical in the plant causing this. The color change isn’t as rapid as in some fungi (psilocybes, some boletes, and some brackets will rapidly change to a dark blue when injured). A couple of the hits I got on them have the roots listed as a folk-medicine with a pronounced sedative effect – one to two drachmas of dried root two to three times a day. That’s a lot of dried roots – almost an ounce a day at the highest recommended dosage.

    A gene survey on these would be interesting. Lynn Margulis is big on the theory (her own) that symbionts exchange genome content and that exchange is a big driver of evolution. I’m really curious if some genes unique to fungi have found their way into the unitropa genome. Whatever chemical is causing that color change seems like it might have its origin in a fungus.

  10. Oh, I would be surprised if they didn’t have chloroplasts – in fact, I would bet that Monotropa have an almost fully functional photosynthetic system.

    My speculation on what probably happened is that the Monotropa ancestors gained the ability to trick the fungi into giving them carbohydrates, and their root system probably had some relatively minor changes. This would have probably been a gradual process, with some speciation along the way.

    Then, in convergent evolution, they started living under low-light canopies, and getting most of their carbohydrates from the fungi. In this case, they could take better advantage of the extensive hyphal network of the trees. Their photosynthetic systems then broke, probably in different ways in different species. This was good and bad. Now they didn’t need to waste energy making leaves/etc but they had to deal with the reactive oxygen species. So they lost the chlorophyll biosynthetic machinery. And eventually, they lost all their above-ground structures except when it was time to produce flowers.

    The reason that I think this photosynthetic breaking probably happened multiple times is that lineages of Monotropa and related mycotropic flowers parasitize specific fungi – whatever signals it’s using for that specific fungus have to be in place before the photosynthetic machinery breaks.

    I would bet you’re correct that there has been some significant genetic transfer from the fungi to the plants.

  11. Hey, think I found a link to the orchid I’d mentioned above—it would be a Corallorhiza—the ones I remember looked like Corallorhiza mertensiana.

    It too is a “myco-heterotroph” just like Monotropa uniflora. So is myco-heterotrophy not beyond Behe’s edge of evolution or do we see some real tinkering here? We know the specification—now how about the complexity?

  12. zylph

    The fungal hosts envelop the roots of unitropa in the same way they envelop the roots of a chlorphyllic plant.

    I believe the simplest explanation for this is that unitropa was once a normal chlorophyllic plant, some fungi that make a living by trading water & minerals for carbohydrates established a symbiotic relationship with it, but unitropa eventually stopped producing carbohydrates and started getting those too from the fungal host. At the same time unitropa retained whatever chemical signature was in place that tells the fungus that unitropa is a symbiont.

  13. Ah, yes, if, as you say, the fungal hosts envelop the roots of unitropa in the same way they envelop the roots of a chlorphyllic plant, if there is no new CSI, then we can chalk this one up to Darwin. And the same thing that happened to Unitropa of the heath family would have happened to Corallorhiza among the orchids—there are other examples too, I believe—the loss of chlorophyll would be no different than the loss of eyes in cave fish.

    So this might provide a nice example where Darwinism is explanatory in contrast to all those areas where it isn’t. Behe might want it in a second edition of his book.

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