Mycoheterotrophic Plants

Nature Talk
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I was delighted to see some Spotted Coralroot plants on the mountain last week and it brought up a couple of questions.

  1. How do plants that fully depend on fungal hosts reproduce? I understand they are flowering plants and require pollinators but after fruiting, how does the new plant find a host and get itself established?

  2. Do they get all of their other nutrients from their host fungi or can they absorb them via their roots?

  3. This hurts my brain a little to think about, but do mycoheterotrophic plants have separate mycorrhizal relationships too?

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Consider that many (if not all) orchids, either mycoheterotrophic or not, need a helper fungus to make their embryos grow. They are almost totally lacking of seed reserves to feed the embryo.

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How do they acquire that fungus?

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Often, the fungal partners are pervasive in the environment. For example, with snowplants (Sarcodes sanguinea), they tap into the mycorrhizal networks in the roots of conifer forests. As long as the snowplants are propagating within the extent of the fungal network they can obtain the sugar and nutrients they need. The fungal network has to be in place first, though. The snowplant won’t survive in its absence.

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Thank you, @screedius!

That takes care of question 1 :)

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Let’s see if I can help with the others. Just note that I am not a plant expert, and we’re making some broad generalizations about mycoheterotrophs that may not necessarily hold true for every single species, so take it with a grain of salt.

The roots of a mycoheterotroph are the part that interfaces with the fungal network, but in the absence of that fungal network, a mycoheterotroph cannot just act like a normal plant and absorb everything it needs from it’s environment through its roots. Mycoheterotrophs are non-photosynthetic, so they need an external sugar source. This is not available in the water and soil, so even if it could get other nutrients it needs directly through it’s roots without a fungal partner, the plant would die without the sugars normally supplied through the fungal network.

I’m not quite sure what you mean by having a separate mycorrhizal relationship. Mycoheterotrophs tap into a preexisting mycorrhizal networks that support other plants. They don’t (as far as I’m aware) develop any secondary mycorrhizal network of their own. The mycorrhizal relationship is a mutualistic one between the fungus and it’s host. Mycoheterotrophs are typically parasites rather than contributors to that symbiotic relationship.