What’s more passive than a mushroom? Unlike grasses that hold their seedheads up high so seeds can hitch a ride on the wind, mushrooms grow close to the forest floor, often half hidden in damp duff. Have you ever wondered how mushrooms spread their spores? A study, presented this past week (on Nov. 25, reported here) at the annual meeting of the American Physical Society’s Division of Fluid Dynamics in Pittsburgh, has an answer: mushrooms make their own wind.
“Wind” may give the wrong impression: more like a light breeze, a draft, a current of air.
Mushrooms contain lots of water, which evaporates through their skins. Evaporation is a cooling process, as the phase change from liquid water to vapor uses up heat energy. Water vapor, being less dense than the surrounding air, tends to rise. The cooled air, being more dense than the surrounding air, tends to sink and spread out. The two forces help carry spores out of the mushroom, and give them a little lift. The spores ride the mushroom’s zephyr across a distance about the width of your hand.
It doesn’t sound like much, but it seems to work. Mushrooms are a species of fungus and there’s a lot still to learn about fungi. There may be a million species out there to study.