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, demonstrates clearly that these fungi also aid in communication.
It joins an established body of literature, recently reviewed in the Journal of Chemical Ecology and in Trends in Plant Science, which has suggested that the mycorrhizae can act as a kind of information network among plants.
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.
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.