Science Finds Plants Have Incredible Human-Like BehaviorsMay 20, 2018
Three and a half decades ago, a book called ‘The Secret Life of Plants’ caused a media storm, claiming that plants had feelings, could telepathize, and even read our minds. So much was the hype that Stevie Wonder even released a soundtrack based on the book, also called ‘The Secret Life of Plants’.
Obviously, this was promptly battered by the scientific community and the idea was laid to rest. But while the idea that plants have supernatural powers may have been pseudoscience, scientists are starting to find that plants also have something similar to “higher cognitive functions” in humans – namely, the ability to communicate and form memories.
Socializing in the Plant World
Botanists now know that plants release chemical signals and react to those that other plants emit. You could call this “communication”, but the latest research suggests they also communicate through sound, just like the way we do when we talk to each other.
One of the earliest to suggest this was a 2012 study that found that young corn plants make clicking noises. When the research team played back similar sounds to the corn roots, they bent their roots in the direction of the sound source.
In a subsequent study on chili seed growth, scientists found that seeds germinated more when other plants were around. In other words, plants were growing more happily with neighbors for company. Because the researchers had blocked communication through light and chemical signals, the best explanation was that the plants were using “acoustic signals generated using nanomechanical oscillations” to tell each other of their presence.
These findings were a welcome surprise to the field, but a question remained – how could plants make sense of the information without a nervous system like animals? Cautious critics pointed out that, for plants to be digesting the meaning of sound, they would have to have sensory mechanisms yet to be discovered.
Evidence to support the sound communication theory have been slowly piling up in the past few years. Research in 2014 showed that plants ramp up their insect defense when played sounds of caterpillars munching on leaves. As well, another researcher proposed a potential mechanism in 2016 that would explain how it works; since certain genes are expressed more in response to specific vibration frequencies, it is plausible that plants react to sound.
Plants also seem capable of forming simple “memories” that help them navigate the harsh realities of plant life. A series of studies showed that plants can learn to make associations, in the same way dogs learn to do tricks with treats.
One study with mimosa plants – which have sensitive leaves that curl when touched or disturbed – tested whether the plants would learn to ignore non life-threatening stimuli.
To do this, the research team dropped plants onto the floor gently and repeatedly to teach them that the impact wasn’t deadly. Though the leaves initially curled, it stopped doing so after a few rounds.
But perhaps the plant just became tired of curling up every so often? To rule out that possibility, the researchers shook the plant soon afterward. The leaves still curled, meaning that they were only responding to the drops. When the researchers dropped the plant a week later, the plants still remembered not to bother curling the leaves.
In another study, pea seedlings seemed to “learn” where a light source was coming from. The study team trained plants to associate light and wind by running a fan from the direction of the light source. After three days of training, they placed the fan and the light in opposite directions and found that plants grew in the direction of the fan, as it had learned.
The question, then, would be this: where are plants storing all the memory without brains? The authors of these studies argue that plants have signaling networks that use calcium molecules; this is similar to the circutry animals use when forming memories. Alternatively, other researchers suggest that plants form “memories” because training triggers sustained changes to the amount of certain molecules in the cell.
In a sense, these new plant findings are humbling: maybe it’s not plants that are similar to humans, but the reverse. What we thought made humans special aren’t necessarily so. At the end of the day, humans are just another species blessed with the miracle of life.