The physics behind fungal spore momentum may not keep all of us up at night, but for a select group of scientists, the issue has proved vexing for over a century.
Now, researchers in the US have solved the mystery of how fungi launch their reproductive seedlings, showing how the merging of minuscule water droplets along the surface of fungal gills can provide enough momentum to shoot tiny spores out into the wide blue yonder.
Given the extreme scale involved here – spores only measure about 10 microns (0.01 mm) in width – you might think the whole study basically redefines minutiae, but that doesn’t mean these spores aren’t in for a wild ride.
“The release of energy is so rapid that it accelerates the entire system with a million Gs, but there’s so much air drag that the spore still only travels a few millimetres at most,” explains mechanical engineer Chuan-Hua Chen from Duke University.
“That’s why it’s so important for the spores to shoot directly away from the fungus.”
The basics of how ballistospores (spores discharged from living beings) are launched has been known for more than a hundred years, after British-Canadian mycologist (fungi biologist) Reginald Buller observed that tiny spheres of fluid forming next to spores were a crucial part of their dispersal.
If these watery spheres – now called Buller’s drops – merges with another drop of water on the fungal surface, Buller hypothesised that the merger released enough surface tension energy to eject a nearby spore into the mushroom-height ether.
Now, for the first time, scientists have been able to observe this phenomenon, recreating the mechanism with a spore-shaped polystyrene sphere standing in for an actual spore.
Positioning their proxy on a flat surface, the team coated the stand-in with a mixture of water and ethanol – just enough to make it cling to the surface by itself.
They then used an ink-jet printer to progressively build up a Buller’s drop beside their spore,…