Researchers Test Fungal Networks

A departure from the bustling, smog filled metropolises that pepper our landscape can usher a peaceable retreat to nature. Rat races towards resource competition and self-gratifying sabotage are exchanged for a system of give and take that ensures harmony for the whole. In this ancient relationship, plants help create a cycle in which all life can foster to grow.

Or do they?

In British Columbia, a silken white flower peeks out of the surrounding brush. Its stems and petals belie a subtle beauty unlike anything else that sprouts around it. But while the pale perennial reaches skyward, surrounding trees gasp for air. Or rather carbon, that is.

The malicious and invisible game of tug-of-war is made possible through a series of underground networks that link this phantom orchid to the rest of the surrounding ecosystem. Because this particular type of flora cannot produce its own energy through photosynthesis, it steals the carbon it requires from nearby trees.

Phantoms aren’t even the only orchid to engage in this kind of chlorophyllic thievery. Many other orchids (known as mixotrophs) remain fully capable of carrying out photosynthesis on their own, yet still continue to pilfer carbon from surrounding plants.

Even these underground hijacking sprees hardly measure up to the dark crimes other seedlings commit beneath the soil.

Rather than merely compete for shared resources, some plants take their will to survive, and thrive, a step further. Instead of petty theft, certain organisms utilize underground connections to deliver toxins to their neighbors in a process known as “allelopathy.”

While the idea of plants spreading viruses to other plants may seem like the stuff of science fiction, it’s actually quite common among trees. Acacias, sugarberries, and more familiar perpetrators such as the American sycamores and a few species of eucalyptus, are all guilty of this.

How is this even possible? Fungus, it turns out.

Everyone is familiar with mushrooms, with their stems and caps serving as the poster children for fungi worldwide. But not unlike the proverbial iceberg, these components are just merely the tip; what sprouts beneath the surface is a vast series of interconnected threading known as mycelium. These threads function as an underground internet of sorts, in which the roots of surrounding plants are linked together.

Nature is not without a parallel series of natural defense mechanisms–which employ these very same mycelium networks to thwart the “cyber” crimes of aforementioned culprits like the phantom orchid and eucalyptus tree.

Ren Sen Zeng of South China’s Agricultural University in Guangzhou made a startling discovery five years ago while studying tomatoes. He grew pairs of these tomatoes in separate pots, allowing some to form mycorrhizae (i.e. fungal networks) while the rest did not.

Once the mycorrhizae were well established, Zeng and his researchers sprayed the leaves of one plant in each pair with a fungus that causes blight disease. Next, air-tight plastic bags were employed to ensure no above-ground chemical signaling could occur between the plants.

Zeng waited patiently for 65 hours before attempting to infect the second plant in each pair. He discovered that those with mycelia were far less likely to get blight. They also sustained substantially lower levels of damage if they did.

He wrote in his report that the research suggested “tomato plants can ‘eavesdrop’ on [defense] signals from the pathogen-challenged” neighbors.

This remarkable form of interplant fungal communication isn’t solely restricted to tomatoes either. David Johnson and his colleagues from the University of Aberdeen demonstrated how broad beans use these networks to warn one another of impending attacks from hungry aphids.

There are even plants that can, essentially, “hack” these networks. Slender wild oat and soft brome harbor the capacity to alter the fungal pathways in the surrounding soil.

Photo courtesy of Wikimedia Commons.

Imagine a natural environment that mirrors the matrix of a computer program, in which all of the living organisms can function as willing programmers. It’s something mycologist Ted Stamets first had an inkling of back in the 1970s. While studying fungi under an electron microscope, he discovered uncanny parallels between mycelia and ARPANET–the US Department of Defense’s earliest version of the internet.

Stamets explained that the fungal networks present in our ecological communities extend far beyond the utilities of attack and defend. Incredibly, nearly 90 percent of land plants exist in a mutually-beneficial relationship with the fungi, which provide them with food, protection from animals, and boosted immune systems.

The mushroom remains a cultural signifier of mystery and power–as a sacred object revered by indigenous peoples, from the atom bomb to collective myths and fables like Grimm’s Fairy Tales. But the real possibilities exist just out of sight, in the secret languages spoken beneath our feet. As we continue to listen in the years ahead, who knows what other startling discoveries they might reveal.

Feature photo courtesy of Daniel Sjostrom.