Saturday, October 31, 2009

A Montana Ghost (Plant) Story

(Halloween issue...)

Howling winds swirl dead, broken leaves all around us. It's late into October, and the time is ripe for a Montana ghost story. Gather 'round and pay close attention because this is a twisted tale of thievery, vegetative vampires, and unexplained underground mysteries -- and it's all happening right now, all around you in our deepest, darkest forests.

These are the family secrets of the four-inch tall "ghost plant" (Monotropa uniflora).

Indian Pipe (Monotropa uniflora)On the surface the ghost plant (sometimes called "corpse plant" or "Indian-pipe") is a modest-looking, flowering plant that shares a common ancestor with the innocent blueberry family. But down below, this furtive family evolved a deceptive lifestyle millions of years ago, back when dinosaurs terrorized the land.

Ghost plants are corpse-white because they have dispensed of the need for green chlorophyll. Instead of making their own food from sunlight and carbon dioxide, they learned how to suck the life-giving fluids from tall trees and lowly fungi living amongst them. It's like a three-way transfusion between a tree, a fungus, and a flowering ghost.

Above ground, a tree grows a massive leaf surface area for collecting sunlight, and uses all of that energy to make sugars. Below ground, a fungus grows a thick mat of tiny hair-like filaments ("hyphae") that are much smaller than the tree's thinnest root hairs, and much more efficient at absorbing water and minerals. So most if not all tree species (and about 90% of all plants) have a mutual arrangement with many fungus species. The fungi are allowed to grow their hyphae deep into the flesh of the tree roots, where they trade some of their minerals for some of the trees' sugars. A single tree might support hundreds of fungi species twisted and tangled around its roots, and those fungi in turn all support the tree. This kind of relationship where both benefit is called "symbiotic."

But the ghost plant is not symbiotic. It is "parasitic," as it steals food from trees and fungi alike. It has no need for sunlight (it's non-photosynthetic), so it thrives even in decaying leaves and mossy logs, deep in the darkest forests where few green plants can survive.

Indian Pipe (Monotropa uniflora)
Using chemical cues, the ghost plant tricks the fungus into treating it like a tree root. The fungus grows its hyphae into the tiny ghost plant seed and starts feeding it minerals. The seed sprouts and the young ghost plant burrows its new roots into the fungus' hyphae. But this trick-or-treat deception goes one step further. The ghost plant also fools the fungus into feeding it some of the sugars that originated in the tree. Apparently, neither the fungus nor the tree get anything in return from the parasitic ghost plant.

After stealing minerals and sugars for months, or even years, the ghost plant rises from the decay and sprouts above ground in late summer or early fall. Insects descend upon the small group of downcast flowers, which turn to face the heavens (and the winds) only after they've been pollinated. Each flower stalk festers into thousands of tiny seeds, each seed consisting of exactly 10 cells -- tiny, because they don't need to store energy with their seeds. The stalks turn black and die, and the seeds scatter on the howling winds.

Look around in the darkened forests, if you're brave enough. These ghosts have all but vanished on the winds once again. But there are thousands of other non-photosynthetic plant species out there, from Montana to Mongolia and everywhere in between. And there are all manner of things in the decomposing leaves under your feet -- living, dead, and otherwise -- that we are barely aware of.

So pay close attention, but leave your garlic and pitchforks at home.
Behind the lens: Okay, so it isn't such a scary photograph. I stumbled across this ghost plant specimen in the damp, dark cedar-hemlock forest surrounding Sprague Creek, in Glacier National Park.