The notion that plants can “talk” to one another was, until relatively recently, dismissed as fantasy, but the reality of inter-plant communication is now becoming an accepted part of mainstream science. A new study shows that trees of different species can exchange large amounts of carbon via the fungal internet that connects their roots. Hidden under your feet is an information superhighway that allows plants to communicate and help each other out. It’s made of fungi.

No tree is an island, and no place is this truer than the forest. Hidden beneath the soil of the forest understory is a labyrinth of fungal connections between tree roots that scientists call the mycorrhizal network. Coined by the journal Nature, the term Wood Wide Web has come to describe the complex mass of interactions between trees and their microbial counterparts underneath the soil. The Wood Wide Web, have allowed scientists to understand the social networks formed by trees underground.

The relationship between these mycorrhizal fungi and the plants they connect is now known to be ancient (around four hundred and fifty million years old) and largely one of mutualism — a subset of symbiosis in which both organisms benefit from their association. In the case of the mycorrhizae, the fungi siphon off food from the trees, taking some of the carbon-rich sugar that they produce during photosynthesis. The plants, in turn, obtain nutrients such as phosphorus and nitrogen that the fungi have acquired from the soil, by means of enzymes that the trees do not possess.

The implications of the Wood Wide Web far exceed this basic exchange of goods between plant and fungi, however. The fungal network also allows plants to distribute resources — sugar, nitrogen, and phosphorus — between one another. A dying tree might divest itself of its resources to the benefit of the community, for example, or a young seedling in a heavily shaded understory might be supported with extra resources by its stronger neighbours. Trimming the small plants has also revealed that the trimmed, stressed plants can send food to healthy neighbours. Even more remarkably, the network also allows plants to send one another warnings. A plant under attack from aphids can indicate to a nearby plant that it should raise its defensive response before the aphids reach it.

Not everything that is transmitted between plants is beneficial to an individual plant, since toxins may also be transported via mycelial networks. The influence of one plant to influence (usually restrict) the growth of another is termed allelopathy, and functions via chemical messengers, e.g. the production of juglone by walnut trees, which was found to reduce the weight of tomato seedlings by about one-third. The whole system is integrated, holistic and complex, and a new area of research has emerged which aims to understand inter-plant communication at the molecular level. It appears that plants may use a form of “language”, in which different molecules act as “words”, although the precise nature of the dialogue has yet to be deciphered.

The implications of inter-plant communication via fungal networks are potentially far-reaching. For example, forest management (harvesting) practices should involve preserving the Mother Trees to nurture new growth. In agriculture, too, practices that leave the mycorrhizal (mycelial) network intact, are thought to aid the absorption of water and nutrients from the soil, and to improve the ability of plants to resist pathogens. Hence the practices of heavy and deep ploughing, which breaks-up the mycelial networks, have been called into question.

The revelation of the Wood Wide Web’s existence, and the increased understanding of its functions, raises big questions — about where species begin and end; about whether a forest might be better imagined as a single superorganism, rather than a grouping of independent individualistic ones; and about what trading, sharing, or even friendship might mean among plants.

I am 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.

Sources: Scientific American, BBC, Resilience, The New Yorker