Researchers at the Radboud University Nijmegen in the Netherlands have found that certain types of plants form underground networks of runners that they use for communication with neighboring plants of the same species. From Science Daily:
Recently [Josef] Stuefer and his colleagues were the first to demonstrate that clover plants warn each other via the network links if enemies are nearby. If one of the plants is attacked by caterpillars, the other members of the network are warned via an internal signal. Once warned, the intact plants strengthen their chemical and mechanical resistance so that they are less attractive for advancing caterpillars.
