Animal advocates and wildlife enthusiasts like you and me are always excited when new research comes out demonstrating the intelligence of the “others” among us; for example, how crows solve problems or whales have complex cultures. But when we cross over into the area of plant intelligence, well, it often sounds a bit too New Agey for most of us.
A recent spate of studies, however, is proving that plants have volition, show altruism and understand kinship much like many animal species. Could this dramatically change how we view plants and, in turn, make us care about what happens to them in the way we’re concerned about threatened, charismatic wildlife?
Moving and mental ability
Four years ago, in 2011, I wrote an article about the intelligent behavior of trees. While those who commented on the blog had mostly positive things to say, social media posters had a field day with the piece. “Nonsense” wrote one and “Having a slow news day?” penned another.
In the years since, however, a number of new studies are continuing to show that plants are smarter than we think. It’s tempting to believe that since plants are rooted in place, they aren’t capable of the complex thought processes that an animal that can run from predators or make its way across town for a cup of coffee is competent enough to achieve. But in a recent article in National Wildlife, author Janet Marinelli cited several reports to the contrary, including one by Italian botanist Stefano Mancuso, a University of Florence professor and plant neurobiology pioneer, who states that just because plants can’t move or run in the way that we do doesn’t mean they aren’t smart.
In 2005, Mancuso and a group of international scientists established The Society for Plant Neurobiology to study sophisticated behavior in plants—much to the jeers of many of their colleagues. By 2010, Mancuso had enough data to give a TED (a nonprofit established to spread new ideas) talk on plant intelligence. In it, he notes that plants are much more sophisticated in sensing what’s around them than animals. Every plant root tip has a tiny region that functions as the locus of electrical signals—the same signals found in human neurons. In essence, every single root apex in a plant’s system can detect and monitor concurrently and continuously at least 15 different chemical and physical parameters. For a plant, a centralized neurological control center (such as a human brain) doesn’t make much sense because a predator—a grazing deer or lawn mower—could easily chop it off. So instead, this decentralized intelligence scattered throughout the roots works as a very effective survival strategy; a plant can persist when even 90 percent of its root tips are clipped.
As for movement, plants do move and they do so with intention. A plant flowers (activity that’s easy to see in time-lapse photography), orients its leaves to follow the light, goes into sleep mode and even “plays” (for visual proof, click on this TED talk link).
Doing the math
Not only do plants engage in neuron-like activity and movement, they make mathematical computations, see us and, like animals that act altruistically, show kindness toward their relatives. They are able to recognize themselves and communicate with animals and other plants via alluring airborne fragrances and a diverse repertoire of chemical compounds exuded through their roots.
In 2013, Antonio Scialdone and fellow scientists at the United Kingdom’s John Innes Centre who were studying Arabidopsis thaliana found that these small weeds in the mustard family are capable of doing some complex arithmetic to prevent starvation at night. Requiring starch to survive, the plants manufacture it by photosynthesizing sunlight. During the night, they measure the amount of starch left in their leaves, use an internal clock to estimate the amount of time until dawn, then divide their food reserve by the expected time to dawn so they have enough starch to last until the sun rises. They’re incredibly accurate: by the time they resume photosynthesis, about 95 percent of their starch has been consumed.
According to Marinelli, in 2012 Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University and author of What a Plant Knows, reported that plants “see” us via photoreceptors that perceive different wavelengths of light. They are aware of when we come near them and whether we’re wearing a blue or red shirt.
In yet another study, in 2007 plant ecologist Susan Dudley of McMaster University in Ontario, Canada, worked with sea rockets—members of the mustard family native to beaches throughout North America, including the Great Lakes—to investigate whether plants can recognize their relatives. Dudley and a graduate student found there was less root competition when closely related “siblings” shared the same pot than when groups of strangers grew in a common container. This demonstrated that the sea rockets not only recognized but acted altruistically toward their relatives, a behavior known as “kin recognition.”
Other studies have indicated that plants are capable of self-recognition. In 1991, researchers Bruce Mahall of the University of California–Santa Barbara and Ragan Callaway, now at the University of Montana, found that the roots of white bursage plants, residents of the Mojave and Sonoran Deserts, inhibited the growth of other plants with which they came into direct physical contact but did not impede the growth of their own roots, meaning that they could distinguish “self” from “other.”
According to the Center for Biological Diversity, of the more than 300,000 known species of plants, the IUCN has evaluated only 12,914, finding that about 68 percent of evaluated plant species are threatened with extinction. Will such new findings on the intelligence of plants cause us to treat them with more respect?
Perhaps your crazy aunt that sings to her plants and way-out-there blog writers who report news about talking trees are on to something after all.
Will a shift in thinking about plants as sentient beings help save them from extinction? Or is plant intelligence research too esoteric to translate into legislative actions?
Here’s to finding your true places and natural habitats,