If you find yourself in Turin, Italy, you might want to take a field trip to the eco-commune of Damanhur. There you can see the 11-story temple it took the 1,000 residents 16 years to build by hand, inspired by a falling star envisioned by the community's leader Oberto Aiuradi (who goes by Falco). You might also want to catch a singing plant concert, wherein sensors attached to the leaves of plants translate some of their biological processes into synthesizer music.
Or, if you don't happen to be going to Italy anytime soon, for a mere $250, you can buy a machine that will allow you to listen into the "music" of your very own houseplants. You've got some options.
What, you may with good reason be asking, is going on here? Plants are silent, unaware, unreactive oxygen factories! They certainly can't make music.
The Secret Life of Plants
That's essentially been the party line on plants for most of recorded history. But then there was that period during the 1970s when Peter Tompkins and Christopher Bird's book "The Secret Life of Plants" made The New York Times best-seller list. The book was chock-full of dubious science experiments: teaching cacti to count and giving houseplants lie detector tests that resulted in the needle of the machine going haywire when a shrimp was boiled alive in its presence, or when a person the plant didn't trust entered the room. There was a lot of talk of "energy fields" and "rays" of one kind or another. But although scientific researchers didn't take the book seriously, and many considered it to have set plant research back a few hundred years, it encouraged the general public to consider plants in ways we never had before.
But with singing plants, we come up against the same kind of questions Tompkins and Bird attempted to answer, albiet using flagrantly unscientific methods. What is the truth about plants? How do they make sense the world? How do they communicate with each other and respond to the myriad of variables their environments throw at them? For a group of organisms that makes up around 99 percent of the biomass on this planet, we actually have very few answers to any of these questions. It's true, the secret life of plants is probably much richer and more complicated than we think. But are plants constantly producing the type of ambient music you normally hear in a day spa?
As you can probably imagine, the short answer to this question is "no."
Transforming Electrical Signals into Musical Notes
Dr. Ratnesh Mishra, a postdoctoral fellow in the Laboratory of Functional Plant Biology at the University of Ghent in Belgium, says in an email interview that the sound we hear as synthesizer music at a "plant concert" at Damanhur comes from movement inside the plant during the cavitation process where air bubbles are sucked up through the body of the plant, especially when water is scarce. It's like having a machine that turns sucking the dregs of your milkshake up through a straw into synthesizer noise.
"Simply put, the machines that translate the 'biofeedback' of plants into music have nothing scientific about them — the whole story has nothing to do with science or the sound of plants," adds Dr. Monica Gagliano, a plant physiologist and associate professor in the School of Biological Sciences at the University of Western Australia. "The apparatus used in many of these instances is a simple multimeter measuring electrical impedance of the plant. The multimeter is then transforming those electrical signals into notes using a sound chip, like those sound cards in your computer, which is how the sounds make sense to our human ears."
Gagliano studies the ways in which plants actually use and interact with sound and, in many ways, her research is right in line with what "The Secret Life of Plants" tried — and spectacularly failed — to do over 40 years ago: to prove that plants have their own version of cognition. According to a 2013 article by Michael Pollan published in The New Yorker, Tompkins and Bird succeeded in not only decelerating research into plant behavior for decades, their book led to the "self-censorship" of researchers who might otherwise have been looking into "the possibility that plants are much more intelligent and much more like us than most people think — capable of cognition, communication, information processing, computation, learning, and memory." Gagliano is one of the few researchers trying to buck the residual scientific stigma around these questions with her research on whether plants can, for instance, learn or demonstrate a their own type of sentience.
One of Gagliano's experiments involves testing how pea plants in dry soil "listen for" and respond to the vibration of moving water. Another study found the roots of young corn plants make "clicking sounds" of around 220 Hz, and respond to clicking sounds emitted at the same frequency.
"Plants have their real sounds and do not need humans to give them fake sounds and say that these are plant's voices," says Gagliano, of the "singing plants" phenomenon. "I could hook you up onto one these multimetres. What if I told you that the sound obtained by translating your electrical impedance was your voice? It would be immediately clear that that is not your voice but a mere sonification of your electrical impedance — nothing to do really with your actual voice or sound."
So, by all means, go to a plant concert — but know that the real voices of plants are much more mysterious than we yet know.