Natural Connections: The purpose of ghost pipe
"Ghost pipe is generally declared a parasite, but radioactive phosphorus first injected into ghost pipe was later found in neighboring trees. Nature is rarely as simple as we think," writes Emily Stone.
CABLE — On one of those drippy, foggy mornings recently, I took a wander down my driveway. The moss on the steep bank was happy at least, although the weather made me feel cooped up. The mosquitoes, too, emboldened by the calm humidity, buzzed too close and triggered a sort of annoyed claustrophobia.
But something glowed in the gloom up under the hemlocks. A cluster of pure white stems beckoned. The cut bank was steep there, the base of the stems at eye level. It took some careful foot placement and big, heaving steps to land myself next to them.
While someone thought that each nodding flower on a simple stem looked like a pipe — hence the name ghost pipe (previously known as Indian pipe) — they make me think of seahorses. The pipe is probably a more accurate shape comparison, but swimming here in the dark, damp shadows under the pines, the luminous, almost translucent clusters of stems feel more like deep sea creatures than inanimate objects.
Ghost pipe is a plant, but these stalks, with their oval bracts climbing upward and the single, bell-shaped flower that emerges directly from the terminus of each stem, have no leaves and contain no chlorophyll.
Chlorophyll, of course, is the green stuff that allows plants to make sugars through the process of photosynthesis. Green plants are known as autotrophs — they produce their own food using carbon dioxide, water and energy from the sun. Auto = by oneself, and trophic = pertaining to nutrition. Like seahorses, ghost pipes are heterotrophs. Hetero = other. They can’t make their own food, and so they must acquire it through the food chain from other plants and animals.
Ghost pipes get their sugars from the trees they live beneath, but the flow of energy isn’t direct. Have you heard of the Wood Wide Web? Beneath the forest duff, 90% of plant species on Earth are in relationships with fungi that extend and connect their roots. Green plants may be able to produce their own sugars, but they need fungi to help them gather water, nitrogen, phosphorus and more.
This mycorrhizal (myco = fungus; riza = root) network is robust and thickly woven. So thickly, in fact, that scientists say you could find seven miles of fungal hyphae in a pinch of dirt, and hundreds of miles under a single footstep.
Ghost pipes engage in mycorrhizal relationships unique to their taxonomic group, where the hyphae of mushrooms form a sheath around the plant’s roots, and then short fungal pegs penetrate the outer cells of the roots. The plant grows finger-like projections around each peg, and the roots become a dense mass that somehow facilitates the grabbing of sugar, water, minerals and more from the mushroom.
Ghost pipes are very picky about who they form this relationship with and seem to connect only to Russula or Lactarius mushrooms. The fungi aren’t so picky, though, and connect also with the roots of pines, oaks, beeches and other trees. The mushrooms provide water and minerals to the trees and receive sugars from the tree in return.
Ghost pipes take advantage of their mutualistic symbiosis, somehow tricking the fungus to channel sugars from the tree into the pure white plant. Ghost pipe is generally declared a parasite, but radioactive phosphorus first injected into ghost pipe was later found in neighboring trees. Nature is rarely as simple as we think.
A few days after spotting those first white flowers, when I shared this relationship with a group of Wisconsin Master Naturalist students, they were indignant. Our culture loathes a mooch. “What good is it?” they asked. “What’s its purpose?”
The purpose of any living thing — at least from its own perspective — is to make more of itself. This flower is surely doing that. I could tell my students weren’t satisfied, though. We’re always looking for a benefit to U.S., or at the very least, a benefit to the ecosystem. “Its beauty isn’t enough?” I countered with a smile.
In fact, that beauty may be important. It improved my mood on a gray morning, but that’s not all. Those luminous white bodies are designed for visibility in the dark woods. The bell-shaped flowers hang down to protect their nectar from dilution by rain. As bees and other insects visit the nectar wells hidden deep inside the flowers, they access sugars created by a tree and dispersed by a mushroom. With their unique lifestyle, ghost pipes are able to bloom in deep woods where little else can.
Who else uses ghost pipe? After I posted my photos from that drizzly morning on iNaturalist, a researcher from Purdue University messaged me asking for help. They have found thrips — small flower feeding insects — on ghost pipes and are trying to discover more about the plant/insect relationship. Under their instruction, I picked a few flower stalks from my woods, packed them in 70% ethanol from the museum’s collections department, and shipped them off on an adventure. Now, we wait for the results.
Meanwhile, the rest of the ghostly flowers in my woods will entice bees to transfer their pollen, raise their flowers up toward the sky, sprinkle their seeds through slits in the blackened, dried-up structures, and stand through the winter as little monuments to curiosity. Surely, we can find some value in that.
Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.
For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The museum is now open with our exciting Growing Up WILD exhibit. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.