Many herbal plants such as strawberry, clover, reed and ground elder naturally form a set of connections to share information with each other through channels known as runners—horizontal stems that physically bond the plants like tubes or cables along the soil surface and underground. Though connected to vertical stems, runners eventually form new buds at the tips and ultimately form a network of plants.
“Network-like plants do not usually produce vertical stems but their stems lie flat on the ground and can hence be used as network infrastructure,” said researcher Josef Stuefer from the Radboud University in the Netherlands.
Stuefer and his team let loose caterpillars on white clover plants and watched them eat a single leaf on the network. Then a second set of caterpillars was allowed to choose between the damaged leaf—one that has been alerted to up its defense status—and leaves from an undamaged network. Over the course of 20 trials, most or all of the approximately 15 caterpillars in each trial preferred the undamaged leaf to the leaf from a damaged network.
“The feeding caterpillars will be deterred and walk off to feed on other non-induced plants,” Stuefer told LiveScience. “[They] understand plant defense language very well as it is directed exactly to them.”
Here is how it works: If one of the network plants is attacked by caterpillars, the other members of the network are warned via an internal signal to upgrade their chemical and mechanical resistance—making their leaves hard to chew on and less desirable.