Plants can communicate the onset of an attack from aphids by making use of an underground network of fungi, researchers have found.
Instances of plant communication through the air have been documented, in which chemicals emitted by a damaged plant can be picked up by a neighbour.
But below ground, most land plants are connected by fungi called mycorrhizae.
The new study, published in Ecology Letters, is the first to demonstrate these fungi also aid in communication.
Researchers from the University of Aberdeen, the James Hutton Institute and Rothamsted Research, all in the UK, devised a clever experiment to isolate the effects of these thread-like networks of mycorrhizae.
The team concerned themselves with aphids, tiny insects that feed on and damage plants.
Many plants have a chemical armoury that they deploy when aphids attack, with chemicals that both repel the aphids and attract parasitic wasps that are aphids’ natural predators.
The team grew sets of five broad bean plants, allowing three in each group to develop mycorrhizal networks, and preventing the networks’ growth in the other two.
To prevent any through-the-air chemical communication, the plants were covered with bags.
As the researchers allowed single plants in the sets to be infested with aphids, they found that if the infested plant was connected to another by the mycorrhizae, the un-infested plant began to mount its chemical defence.