Tree live simple lives- or so we may think; nothing to do all day but stand in the sun with their feet in the damp soil. However, we can probably all agree that there is more to their lives than meets the eye. We tend to think of plants as competing individuals whose only goal is to keep themselves alive and reproduce. Life can be thought of as a competitive force where hordes of creatures are all after the same things, and mostly live directly at the expense of others. But life is also inevitably cooperative. Trees are great competitors but they are also some of the best cooperators. We know they form an array of mutualistic relationships with a variety of creatures from bacteria and fungi that help them transfer nutrients to the many kinds of animals that help them carry out their reproduction in different stages. To us, trees do not seem to be aware as you or I or monkeys or dogs. They do not have brains. But they are sentient in their own way; they gauge what is going on and react accordingly. But do they communicate to one another?
The evidence for plant communication is only a few decades old, but in that time has jumped back and forth between provocative discoveries to flat out debunking. A study published in 1983 by Professor Gordon H. Orians, University of Washington showed that Willow trees, Poplars, and Sugar Maples can warn each other about insect attacks. Healthy, unaffected trees near ones that are infested with hungry bugs begin pumping out bug-repelling chemicals to ward off attack. They somehow know what their neighbors are experiencing, and react to it. The awakening implication was that these brainless trees could send, receive, and interpret messages from one another. It is now well known within the scientific community that when bugs or other herbivores chew leaves, plants respond by releasing volatile compounds in the air. More recently there are handfuls of studies of plant communication which confirm that other plants detect these airborne signals and ramp up their own chemical weapons or other defense mechanisms in response. Plants can communicate with insects as well, sending airborne chemicals that act as distress signals to predatory insects that kill herbivores.
Scientists are also exploring how the messages from these signals might spread. How does the leaf know it is being eaten and tell other parts of the plant to start pumping out defense chemicals? Aside from using chemical signals in the form of organic compounds, recent research from biologists have discovered that some flowers use electrical fields to communicate with insects. The shape of a flower, its color, and scent attract bees and flies to pollinate the plant. However recent studies also show that electricity is also a component used in these species of flowers to communicate with other organisms. The Swiss Biologist, Ted Farmer, discovered through a study that plants share information with electrical pulses; strangely reminiscent of the animal nervous system. This study did not conclude that plants have neurons, or brains, or anything like the systems that we as animals use to communicate but merely indicated the hidden complexity of these organisms. The reality may be that we are not doing any justice to plants when we try to put their amazing biology in to human terms but the study does strongly suggest that we may have clearly underestimated their capabilities.
New studies seem to bring us closer to understanding the plant world; though each new discovery erodes a little more of what we thought we knew about what plants do and what they are capable of doing. It may actually be that in order to learn what else they are capable of, we have to stop anthropomorphizing plants altogether. Maybe instead, we need to try to think like them. Imagining what it is like to be a plant could be the key to understanding why they communicate or simply behave; or possibly show us how to live and design with plant species more intelligently.
For more information on plant communication, check out Plant Talk at www.the-scientist.com.
For an example application of how understanding plant messaging could benefit us, see this online article from Cornell University.