A new book, The Secret Life of Trees, titles that trees talk to one another. But is this actually the case? The humble answer is that plants surely give-and-take information with one another and other organisms such as insects. Think of the scents of recently cut grass or crushed sage. Some of the chemicals that produce these aromas will tell other plants to get ready for an attack or summon destructive insects to defend them. These evocative smells could be understood as cries of warning or shouts for help.When plants are injured by infection or by being eaten, they discharge a variety of volatile molecules into the air around them. After contact to some of these chemicals, close plants of the similar species and even other species become fewer vulnerable to attack, for instance by making toxins or substances that make themselves tougher to digest.
These changes do not generally happen instantly but the genes needed to turn on much more rapidly when they are necessary. There is also evidence that the chemicals discharged by plants in a specific location are slightly different from those discharged elsewhere by the similar species. Thus, it appears that if plants talk, they even have languages or at least regional inflections.
But is this true communication, as humans know it? It really is not clear whether a plant releasing chemicals means to pass on information to another plant by doing so. I answered to the chemicals released by frying onions but that does not mean that the onions are speaking to me. So are these really messages or just the opportunist usage of chemical information in the environment? It appears possible that these signals started out not as a manner to send information to other trees but to get messages rapidly and efficiently to other parts of the similar plant. Pests or infections will often move from one branch of a tree to the ones next to it.
But a warning telling every individual branch to get ready for an imminent attack might have to move most of the way through the tree and then back up it if the communication had to move through the body of the plant. This could be a trip of tens of meters in a tall tree. A signal that can move through the air, meanwhile, can go straight to the branches closest to the attack. An importance of these unstable signals, still, is that they can be 'overheard' by every plant the chemicals reach. So when other trees answer by also beefing up their defenses, is it communication or snooping?
Maybe it is a bit of both. Perhaps an interior messaging system became co-opted to relief plants near enough to 'listen in' as they would often be connected to the tree sending the message in a standard illustration of evolutionary 'kin selection'.
Though releasing chemicals into the environment is accepting and other plants and organisms can take benefit. Occasionally these chemical 'messages' can draw pests or parasites. The smell of crushed sage does not defend it from humans, for example... rather the opposite. Not all transmission of information between plants is through the air. The massive majority of plants live in cooperative relationships with soil fungi.
We tend to consider forest fungi as mushrooms and fungus above the ground but these only arise after sexual re-production. The actual fungus is a rug of extended cells scattering through the forest floor. The trees deliver the fungi with sugar and the fungi support the tree to collect water and soil nutrients. And numerous plants can be combined underground by cells of the similar individual fungus.
Occasionally when one plant undergoes damage, other plants joined to it through their soil fungi defend themselves against future attacks though other plants similarly near that are not 'plugged in' don’t. This fungus network is another transferor for information, a true Wood Wide Web.
But who is in control? The messages are communicated by the fungus and maybe it is the one actually using the information, collecting it from one of its host plants and transferring it on to the others to protect its 'revenue'. The fungus supports the plants to communicate but may do it for its own resolves, and that might contain especially helping its best producers, whether they are related to the tree transferring the message or not.
Information planned for family and friends may result in being passed on to unconnected third parties to profit the transferor of the message. In this way, fungi are a bit similar to a social media company, listening into and helping from its users’ posts.
So we return to the problem of whether any of these examples are communication in the logic that we would mean it. Whatever that makes people think more about plants is decent, but maybe making trees seem more like us can lead us to watch their important nature. As a faintly hippy student, what fascinated me to plant science was the technique that trees and other plants fluidly modify to their environment. Maybe using the chemicals that reach them to form their adaptation is just another face of this. Worrying about whether trees communicate really says more about us than them.
Stuart Thompson, Senior Lecturer in Plant Biochemistry, University of Westminster.
This article was originally written on The Conversation.