A new book, The Hidden Life of Trees, claims that trees talk to one another. But is this really the case? The simple answer is that plants certainly exchange information with one another and other organisms such as insects. Think of the scents of newly mowed grass or crushed sage. Some of the chemicals that make up these aromas will tell other plants to prepare for an attack or summon predatory insects to defend them. These evocative smells could be seen as cries of warning or screams for help.
When plants are damaged by infection or by being eaten, they release a range of volatile molecules into the air around them. After exposure to some of these chemicals, nearby plants of the same species and even other species become less vulnerable to attack, for example by producing toxins or substances that make themselves harder to digest. These changes don’t usually happen straight away but the genes needed turn on much more quickly when they are needed.
There is also evidence that the chemicals released by plants in a particular location are subtly different from those released elsewhere by the same species. Consequently, it seems that if plants talk, they even have languages or at least regional accents.
But is this really communication, as humans understand it? It really isn’t clear whether a plant releasing chemicals intends to pass on information to another plant by doing so. I respond to the chemicals released by frying onions but that doesn’t mean that the onions are talking to me. So are these really messages or just the opportunist use of chemical information in the environment?