No, it's not a typo. American biologists have discovered that a common corn fungus is able to blast its spores with an acceleration equivalent to 870,000g (1g is the acceleration caused by Earth's gravity). According to this Duke University news release, "Corn fungus is nature's master blaster," this acceleration breaks the previous natural record by two orders of magnitude. And these spores also travel much faster than rifle bullets, but they don't go very far, stopping after only 5 millimeters. Is this discovery important for us? Probably not, but this is another story for the fungus. Moving away from the parent, the spores can get into air currents and acquire their independence. Read more.
Let's start with a picture. The illustration below describes the launching devices of three different organisms (Credit: Steven Vogel).
The fungus Pilobolus is shown with the sporangium on top of the subsporangial swelling just before it shoots upward on a jet of cell sap. Sphaerobolus appears just before and just after a global mass of spores gets sent aloft by eversion of the floor of the cup. The seed Ruellia has been caught just before the end of launch, with each seed propelled upward by motion of the ejaculator beneath it.
Now, why are biologists studying such a phenomenon? Here is the explanation from the Duke University news release -- obviously not written in plain English.
The purpose of the study that revealed the fungus's extraordinary launch capabilities was to better understand the biological mechanism behind the fungal supergun.
Basically, the gun is powered by the buildup of pressure inside the spore-containing fungal fruiting body, called the perithecium, due to the ability of sap to create an osmotic pressure. Such pressure is due to water flowing across a membrane into the perithecium as it tries to equalize the concentration of a salt solution inside the chamber. In the case of the fungus, at question was whether the sugar mannitol or potassium ions were responsible for the osmotic pressure that generated the propulsive force.
The researchers -- Frances Trail and Iffa Gaffoor of Michigan State University, and Steven Vogel of Duke University have published their findings in the scientific journal Fungal Genetics and Biology (Volume 42, Issue 6, Pages 528-533, June 2005). Here is a link to the abstract of this paper named "Ejection mechanics and trajectory of the ascospores of Gibberella zeae (anamorph Fuarium graminearum)."
Usually the scenery about them is drear and savage enough; and the logger’s camp is as completely in the woods as a fungus at the foot of a pine in a swamp; no outlook but to the sky overhead; no more clearing than is made by cutting down the trees of which it is built, and those which are necessary for fuel.
—Henry David Thoreau (1817–1862)
One of the researchers, Steven Vogel, has recently written another paper on the subject, which has been accepted by the Journal of Biosciences, a quarterly journal published by the Indian Academy of Sciences, Bangalore. Here is a link to the full paper named "Living in a physical world: III. Getting up to speed" (PDF format, 10 pages, 278 KB). This article contains a table giving the accelerations for a large variety of biological projectiles. The image above comes from this paper.
And here is Vogel's conclusion about the Gibberella zeae, the nature's most powerful known cannoneer.
"An obvious question is why the fungus even bothers. Given the short range of its spores, why bother accelerating to eighty miles per hour to go a mere five millimeters?," said Vogel. "Since there is almost no air movement at the surface where the spore grows, the real object of the launch is to get the spore even a little ways from the parent, so that it can get into air currents, which will really give the spore some range."
It seems than even for fungus, kids need to run away from their parents.
Sources: Duke University news release, via EurekAlert!, July 25, 2005; and various web sites
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