Monday, March 30, 2009

Velvety Underground

I’m sorry I missed February, but I started the in-depth work on my thesis, which makes it difficult to get into the blogging mindset. However, I have found another parasite that has managed to get listed1. They live on the bodily fluids of a single species, rarely even seeing the light of day. After that description, I want you to imagine an orchid.
Now, look at this picture.

Image from ARKive
Image from ARKive

This is the Underground Orchid (Rhizanthella gardneri). While many orchids are parasitic—living as the botanical equivalent of a louse—they produce pretty flowers, so no one thinks twice about trying to save them. The Underground Orchid’s lifestyle is not much different, except for the fact that it looks like a root with a tumor. It lives in the root system of the Broom Honey Myrtle, a pine-like tree from Australia. This orchid produces no chlorophyll, because that would be pointless if the flower might break the surface. Instead, it gets its energy and nutrients from the Myrtle, but it’s not as simple as that. It never is.

I had originally thought that parasitic plants work by putting its roots into the roots of the host and effectively sucking the tree’s blood. Some do. The Underground Orchid, however, is myco-heterotrophic. This means that there is a fungus living in the Myrtle’s roots, sucking out its juices. The orchid then subsists on the juices of the fungus, making this some sort of strange nesting-doll version of parasitism2. The end result is still the orchid parasitizing the tree, but with some (unwilling) help from a root fungus.

The Underground Orchid relies on the existence of the Broom Honey Myrtle, and tracts of these trees are being cleared to make way for agriculture. People are also attributing a decrease in health of the myrtle to a decrease in the numbers of the orchid. Preservation sites are being set up throughout the Underground Orchids’ range to help save them. Also, botanists are also working on finding a way to breed these root-flowers in captivity.

1Just so you know, the Pygmy Hog-Sucking Louse managed to get a mention on QI.
2I’m sure there is some Australian burrowing insect that would suck the juices out of the orchid, making this even more recursive.