tangledwing:

Microscope image of mycorrhizae Mycorrhizae are mutualistic - they both need and are needed by the plants whose roots they inhabit.
Plants can communicate the onset of an attack from aphids by making use of an underground network of fungi, researchers have found.

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.

The plants and the fungi manage tmicroco do this without neurons, i.e. brain cells.
