Vortex rings are the fluid phenomena that allow jellyfish and squid to move swiftly and gracefully through the water. They are what we form when we blow smoke rings (also demonstrated at this great Exploratorium exhibit). And they are how some mosses release their spores to reproduce.
That’s according to scientists Dwight Whitaker and Joan Edwards, who published a paper on Sphagnum moss in today’s issue of Science.
Sphagnum moss (also known as peat moss) forms thick mats covering approximately 1 percent of Earth's land surface and is important in the global carbon cycle, potentially storing more carbon than any other plant genus. To reproduce, the ground-hugging moss must launch its spores high enough to be picked up by wind and carried long distances.
Per the Not Exactly Rocket Science blog in Discover:
They are among the most common plants in the world, growing in the cold, moist parts of the Earth and covering about 1% of its land. They rely on the wind to disperse their spores and all of them face a similar problem. They grow in flat mats, which hug the ground at a level where the air is relatively still.
So they grow close to the ground but need height (10 centimeters, or almost 4 inches) to disperse their spores. How to get that high? Those aforementioned vortex rings. The two researchers used high-speed cameras to capture the release of the spores and catch the mushroom-cloud vortex rings in action.
The Nature blog The Great Beyond shows two of the videos (be sure to watch them both). The blog also describes the process:
So how does this blast happen? As wet, spherical Sphagnum capsules dehydrate in the sun, the pressure inside them increases and they start to become more cylindrical. At some point, the pressure causes the capsules to burst—a process that only takes a fraction of a second. Since the capsule is cylindrical and pressurized at this critical moment, the spores get launched vertically.
And fast, too. According to Discover:
The spores are ejected at around 30 miles per hour at around 32,000 times the force of gravity.
Cool! We tried to reach our own bryophyte expert, Jim Shevock, to comment about this finding. But he’s moss-hunting in China’s Sichuan Province right now. We’ll have to wait until he returns to get his thoughts on this spiffy spore spectacle.
Creative Commons image by David Paloch