Last summer I hacked away at an old tree stump. At night, the wood chips glowed. What caused this?
—Ron Hay, Trent-Severn Waterway, Ont.
No need to call Ghostbusters: A fungus that infests trees likely caused the glow, says Sylvia Greifenhagen of the Ontario Forest Research Institute. The phenomenon is called bioluminescence: the emission of light by a living thing.
She suspects your fungus was of the genus Armillaria, the most common group of glowing fungi in Ontario. Along with dead wood, Armillaria invades the roots of live trees, sometimes moving up through the stump and lower trunk, causing decay. “A healthy tree is usually able to keep the fungi at bay,” Greifenhagen explains, “however, if it’s compromised in some way, the fungus has a better chance of gaining a good foothold.”
The fungus sends out tiny, thread-like strands called mycelia to invade the wood; these glow. Researchers are still studying the science of glowing fungi, but they know that it involves luciferin (diabolical!), a light-emitting molecule apparently found in most organisms that bioluminesce, and luciferase, an enzyme that catalyzes the chemical reaction producing the light. Bioluminescent fungi emit light continuously, but you only saw it after you exposed the mycelia.
The light will last for a few weeks, says Greg Thorn, a biology professor at the University of Western Ontario, because the fungus needs moisture. “As the wood and the fungus dry out, the mycelia will stop glowing.”
Scientists know why some organisms bioluminesce. For example, fireflies signal mates. “But nobody really knows why the mushroom does it,” says Thorn. “What is a mushroom signalling?”
Possibly insects, at least in some cases of glowing fungi; one theory is that insects help to spread fungi spores.
Published in the June 2011 issue of Cottage Life