They look so helpless tied to the soil. Plants and fungi, however, have perfected technologies for spreading themselves far and wide. Their arsenal includes “short-range, intermediate-range, and long-range microballistics,” says Nicholas P. Money in the journal Current Biology. Take a look inside the armory:

For very small projectiles, like fungal and plant spores, the only way to escape a surface is to rocket off at an incredible speed at the get go. Even with an initial burst of momentum, many spores travel no farther than a few times their own cell length before viscous drag brings them to a dead stop and they float to the ground…. Greater discharge distances, ranging from tens of centimeters to meters, are achieved by ejecting spores with pressurized fluid (many fungi), the use of an air gun (Sphagnum moss), and a unique snap-through buckling mechanism (the artillery fungus). [Emphasis added.]

Short-Range Missiles

Some fungi use the dandelion-seed method of letting go of the spore and letting the wind take it wherever it can. One named Deightoniella, however, explodes its spores with finesse. It “makes use of explosive bubble formation, or cavitation, within its stalks to launch its spores,” relates Dr. Money. Here’s what happens as the spore bulb at the tip of a stalk dries out:

Cavitation relieves the negative hydrostatic pressure that develops when water evaporates from the cytoplasm of the cell with a thick cell wall that resists collapse. The stalk cells of another fungus, Zygophiala, bend as they lose water and straighten with the formation of cavitation bubbles. Bending of the stalk cells occurs over a few seconds and straightening happens in microseconds.

The explosive bubbles are enough to send the spores 15 times their own length. At just a few millimeters, that’s far enough to escape the boundary layer of still air on the leaf surface where they grow. Mushrooms, by contrast, use condensation rather than evaporation, employing the properties of surface tension as water droplets snap together. It’s a very effective technology:

There are no comparable mechanisms elsewhere in nature. Using this catapult, as many as 30,000 sporesrelease themselves from the gills of a mushroom every second, corresponding to billions of spores over the lifetime of the fruit body.

Intermediate-Range Missiles

Some plants launch their payloads up to several centimeters. Ferns, for example, launch spores with a “miniature slingshot” that also relies on cavitation, says Professor Money. Like some animals that use “latch-mediated spring actuation mechanisms” to achieve some of the fastest accelerations in biology, ferns can expel spores at 10 m/s in just 30 microseconds.

Sphagnum moss, ascomycete fungi, and “pollen catapults” in some trees launch their DNA even faster. This part of the article shares astounding feats of lowly fungi and plants. Here are a couple of examples to marvel at:

High-speed video clips of ascus discharge recorded at 1 million frames per second have clocked a maximum launch speed of 32 m s^-1 from a fungus called Neurospora tetrasperma (Figure 4A). The spores reach this speed as soon as they slip from the tip of the ascus, which takes a few microseconds and involves tremendous acceleration. Hydra nematocysts are even faster: their stylets are fired at a speed of 19 m s⁻¹, with an estimated acceleration of 5 million g, and stop dead within a microsecond. Even so, ascospore discharge is certainly among the swiftest movements in biology. Spore rotation is another amazing metric. The ellipsoidal spores of Neurospora spin end over end during flight at a rate of 40,000 revolutions per second, or 2 million revolutions per minute. Although the difference in size and duration renders the following physical comparison frivolous, these spores spin faster than neutron stars.

The technologies used in these organisms include turgor pressure, springs, latches, compressed air, pressurized fluid, hinged lids, reinforced rings, unfolding sleeves, and more, with careful tuning of osmotic pressure, vapor pressure, and other physical forces. “The motion of the dogwood anther,” the author quips, “is like the arm of a baseball pitcher.”

Long-Range Missiles

Organisms that can hurl their payloads as far as meters run into air resistance and gravity. Dr. Money mentions a tiny fungus named Pilobolus (“hat thrower,” picture above) can send its spores 2 meters using a “miniature squirt gun” after generating 5 atmospheres of pressure inside the device. He also mentions the “artillery fungus” Sphaerobolus whose ejection apparatus resembles the Venus flytrap or a jumping popper toy. This genus can eject its spores 6 meters. Sascha Pare at Live Science tops that, describing the “squirting cucumber” that can propel its seeds 33 meters “with remarkable speed and precision.” 

Isn’t Evolution Wonderful?

Both writers claim these technologies “have evolved” presumably by sheer dumb luck over millions of years. Pare quotes a biologist who maintains that “The explosive launch of the cucumber plant has evolved over generations to help it survive.” And Professor Money ends his piece,

The ballistic mechanisms that have evolved among fungi and plants are united by the movement of water, either by osmosis to pressurize the cytoplasm, condensation to create mobile droplets, evaporation to deform elastic cell walls, or the impact of raindrops. In the absence of musculature, these hydraulic processes are the only way to power the propulsion of spores, pollen, and seeds through air.

Like flies in the soup or smoke in the eyes, these statements are unwelcome additions to a fascinating biological tour.