Bean's Talk:  

The Economist has an article on "nature's internet" - the ability of plants to communicate via mycellium - the roots of mushrooms - Bean's Talk.

THE idea that plants have developed a subterranean internet, which they use to raise the alarm when danger threatens, sounds more like the science-fiction of James Cameron’s film “Avatar” than any sort of science fact. But fact it seems to be, if work by David Johnson of the University of Aberdeen is anything to go by. For Dr Johnson believes he has shown that just such an internet, with fungal hyphae standing in for local Wi-Fi, alerts beanstalks to danger if one of their neighbours is attacked by aphids.

The experiment which suggests this was following up the discovery, made in 2010 by a Chinese team, that when a tomato plant gets infected with leaf blight, nearby plants start activating genes that help ward the infection off—even if all airflow between the plants in question has been eliminated. The researchers who conducted this study knew that soil fungi whose hyphae are symbiotic with tomatoes (providing them with minerals in exchange for food) also form a network connecting one plant to another. They speculated, though they could not prove, that molecules signalling danger were passing through this fungal network. ...

Broad beans, then, really do seem to be using their fungal symbionts as a communications network, warning their neighbours to take evasive action. Such a general response no doubt helps the plant first attacked by attracting yet more wasps to the area, and it helps the fungal messengers by preserving their leguminous hosts.