Plants talk to each other using an internet of fungus
By Nic Fleming -- 11 November 2014
While mushrooms might be the most familiar part of a fungus, most of their bodies are made up of a mass of thin threads, known as a mycelium. We now know that these threads act as a kind of underground internet, linking the roots of different plants. That tree in your garden is probably hooked up to a bush several metres away, thanks to mycelia.
The more we learn about these underground networks, the more our ideas about plants have to change. They aren't just sitting there quietly growing. By linking to the fungal network they can help out their neighbours by sharing nutrients and information – or sabotage unwelcome plants by spreading toxic chemicals through the network. This "wood wide web", it turns out, even has its own version of cybercrime.
Around 90% of land plants are in mutually-beneficial relationships with fungi. The 19th-century German biologist Albert Bernard Frank coined the word "mycorrhiza" to describe these partnerships, in which the fungus colonises the roots of the plant.
In mycorrhizal associations, plants provide fungi with food in the form of carbohydrates. In exchange, the fungi help the plants suck up water, and provide nutrients like phosphorus and nitrogen, via their mycelia. Since the 1960s, it has been clear that mycorrhizae help individual plants to grow.
Fungal networks also boost their host plants' immune systems. That's because, when a fungus colonises the roots of a plant, it triggers the production of defense-related chemicals. These make later immune system responses quicker and more efficient, a phenomenon called "priming". Simply
plugging in to mycelial networks makes plants more resistant to disease.
But that's not all. We now know that mycorrhizae also connect plants that may be widely separated. Fungus expert
Paul Stamets called them "Earth's natural internet" in
a 2008 TED talk. He first had the idea in the 1970s when he was studying fungi using an electron microscope. Stamets noticed similarities between mycelia and ARPANET, the US Department of Defense's early version of the internet.
Film fans might be reminded of James Cameron's 2009 blockbuster
Avatar. On the forest moon where the movie takes place, all the organisms are connected. They can communicate and collectively manage resources, thanks to "
some kind of electrochemical communication between the roots of trees". Back in the real world, it seems there is some truth to this.
It has taken decades to piece together what the fungal internet can do. Back in 1997,
Suzanne Simard of the University of British Columbia in Vancouver found one of the first pieces of evidence. She showed that
Douglas fir and
paper birch trees can
transfer carbon between them via mycelia. Others have since shown that plants can exchange nitrogen and phosphorus as well, by the same route.
Simard now believes large trees help out small, younger ones using the fungal internet. Without this help, she thinks many seedlings wouldn't survive. In the 1997 study, seedlings in the shade – which are likely to be short of food - got more carbon from donor trees.
"These plants are not really individuals in the sense that Darwin thought they were individuals competing for survival of the fittest," says Simard in the 2011 documentary
Do Trees Communicate? "In fact they are interacting with each other, trying to help each other survive."
