Ariel Novoplansky, an ecologist in Israel, set up an experiment among pea plants to study how they communicate with each other.

In the experiments, Ariel put the pea plants in rows of containers. The center plant in the row was the target. The pea plants had been grown with two main roots. On one side, each pea plant had one root in its own pot and the other reaching into a neighbor's pot. The central plant connected to its closest neighbor, which connected to another neighbor, and so on down the line. On the other side, all the plants kept their roots in their own pots, unconnected to their neighbors.

With everything ready, the ecologist created a dryness for the central target plant, which had quickly closed up its leaf pores(气孔)to save water. Amazingly, the connected plants on one side gradually closed up their leaf pores, even though only one of them had experienced real dryness. On the other side, with unconnected roots pea chain, all their pores stayed open. This means the warning signal didn't travel from the stressed plants leaves through the air, but only from its roots through the soil.

It's possible that plants are just eavesdropping (偷听) even if the damaged plant didn't mean to send signals to them. Maybe the damaged plant leaks certain chemicals and nearby roots could sense those signals. But the plants with connected roots that weren't dried out passed on the drought signals to their neighbors too, which means simple eavesdropping probably isn't the answer. They seem to be having a real conversation, picking up information on one side and sharing it with a neighbor on the other.

The benefit to a plant that receives this information is pretty clear. But what's the benefit to sending a danger signal to your neigbour? Remember, your neighbor may actually be you.