Plants use underground networks to communicate danger

It is fascinating that different individual plants can be connected to one another by underground fungal networks and it is even more amazing that plants may use these connections as early warning systems of aphid attack.

Plants use underground fungal networks to warn their neighbours of aphid attack, scientists from the University of Aberdeen, the James Hutton Institute and Rothamsted Research have discovered. The study, published in Ecology Letters, is the first to reveal plants’ ability to communicate underground in this way.

The research changes our understanding of the ways in which living things interact with one another. If crops can be managed in a way that exploits this natural communication channel, it could provide a new weapon in the battle against insect pests.

Scientists grew the bean plant (Vicia faba) in groups of five. They allowed three in each group to grow underground networks of mycelia – a thread-like fungus that grows from one set of roots to another. They kept the two remaining plants free of the fungal links. They then infested one of the plants in each group with aphids, triggering the release of a suite of chemicals designed to repel aphids but attract wasps, one of the aphid’s predators.

Remarkably, plants which were not under attack themselves, but which were connected to the victim by the underground fungal network, also began to produce the defensive chemical response. Unconnected plants didn’t mount a chemical defence, so remained vulnerable to aphid attack. Previous research had shown that plants could communicate chemically through the air, but the researchers covered the plants with bags to rule out above-ground signalling.

Dr David Johnson, of the University of Aberdeen, led the study. He said: “We knew that plants produce volatile chemicals when attacked, and we knew they communicate danger to each other above ground. Now we know that they communicate danger through these underground fungal networks as well. Connected plants that weren’t infested by the aphids behaved as though they were. We don’t quite know the mechanism, but it’s likely to be a chemical signal. Our understanding of ecological systems has not considered the fact that plants are interconnected in this way. It could have major implications for our understanding of how one organism affects another.”

Dr Lucy Gilbert, senior ecologist at the James Hutton Institute and co-author of the study, commented: “It is fascinating that different individual plants can be connected to one another by underground fungal networks and it is even more amazing that plants may use these connections as early warning systems of aphid attack. Our research indicates that these connections, by being a conduit for signals between plants, affect the plants, the aphids and the parasitoids that are enemies of the aphids. This may have implications for crop pest control. The next research challenge is to identify the signalling compound being transported through the fungal network.”

Another of the study’s authors, Professor John Pickett of Rothamsted Research, said: “Aphids affect all higher-latitude agricultural regions, including the UK, the EU, North America, and North East Asia. This research could provide a new, sustainable and natural intervention. In a field of plants that have some inducible resistance to aphids, we could use a plant that’s susceptible to aphid attack to ‘switch on’ the defence mechanism through the natural underground connection. There’s the potential to deal with other pests and diseases, in other regions, in a similar way.”

Notes for editors

Paper: Underground Signals carried through common mycelial networks warn neighbouring plants of aphid attack’. 2013. Ecology Letters. (doi:10.1111/ele.12115)