The secret social lives of plants

Contrary to the long held idea that plants are un-communicative, recent research has made it clear that they do in fact conduct informative exchanges between themselves. Film fans might be reminded of the 2009 blockbuster Avatar. On the moon where the movie takes place, all the organisms are connected. They can communicate and collectively manage resources, thanks to “electrochemical communication between the roots of trees."

Tree of souls....Avatar

Although the general theory of plant communication is not new – plant scientists discovered it in the 1980’s – more accurate experimentation is now helping us understand more about how and why they communicate. And it is certainly more then mere gossip, but an important means of spreading news about danger.

The ability to no only react to danger but to warn others of it has been a controversial finding, suggesting that a brainless tree can not only send and receive messages, but interpret them as well. Despite the growing evidence that plants are capable of communication, many plant scientists still question whether this cross talk is biologically meaningful. No experiment has yet demonstrated that the signalling between neighbouring plants can benefit the emitting plant, prompting some researchers to suggest that “eavesdropping” is a more accurate description of what has been observed than “intentional” communication.

This diagram displays how plants communicate. It is not only hungry animals they have to be aware of, but insects too! Source: Logan Parsons, The Science Magazine

Back on on earth, scientists have revealed that plants communicate through the air, by releasing odorous chemicals called volatile organic chemicals (VOCs), and through the soil, by secreting soluble chemicals and transporting them along thread-like networks formed by soil fungi. It turns out almost every green plant that has been studied releases its own cocktail of these chemicals, and many species pick up and respond to the various messages. As an example, the smell of cut grass — a blend of alcohols, aldehydes, ketones and esters — may be pleasant to us but to other plants signals that danger is on the way. 

Wouter Van Hoven, a zoologist from Pretoria University found that when Acacias were nibbled on by antelope, they produce leaf tannin quantities that are lethal to the browsers, forcing them to move on, and in addition the acacias emit ethylene into the air, which warns other trees of the impending danger. Trees up to 50 yards away then react to this message and step up their own production of leaf tannin within just five to ten minutes. You don’t need to be a scientist to see this in action…next time you are watching giraffe, notice how they tend to feed in the opposite direction of the wind, avoiding the bitter leaves from trees that have been pre-warned and already upped their tannin levels! The defensive compound that gets emitted from the leaves is called Jasmonic acid, providing the name “Jasmonation” to the process of the tree’s talking to each other.