The science investigating consciousness and intelligence in plants is a fascinating and rapidly developing field of study. The bias in which all intelligent life forms require a brain and “standard” nervous system is in the process of being debunked. Vegans, beware: cruelty-free living is, alas, impossible! However, increasing awareness of all life forms does allow us to make better choices, gives us all an opportunity to be grateful, and to realize that to be alive is to cause some degree of harm to other beings. I do love plants very much, and I feel a great affinity with them. As an amateur gardener, I am frequently impressed by the survival strategies of plants, and how they sometimes compete with one another, and sometimes cooperate…not unlike us humans!
Michael Pollan, author of the Omnivore’s Dilemma and The Botany of Desire, among other titles, published a highly informative article on the subject describing recent developments in plant science in the New Yorker on December 23, 2013 called The Intelligent Plant. I have read portions of “The Secret Life of Plants”, mentioned in the opening remarks of Mr. Pollan’s article. Like him, I was deeply intrigued by the experiments with plants and polygraphs conducted by former CIA polygraph expert Cleve Backster, in which events from distances of several hundred miles, plants were recorded registering a variety of responses to various thoughts and stimuli. Pollan pursues that the 1973 title compiled a “beguiling mashup of legitimate plant science, quack experiments, and mystical nature worship that captured the public imagination at a time when New Age thinking was seeping into the mainstream.” Here is a quote from the article:
“Backster and his collaborators went on to hook up polygraph machines to dozens of plants, including lettuces, onions, oranges, and bananas. He claimed that plants reacted to the thoughts (good or ill) of humans in close proximity and, in the case of humans familiar to them, over a great distance. In one experiment designed to test plant memory, Backster found that a plant that had witnessed the murder (by stomping) of another plant could pick out the killer from a lineup of six suspects, registering a surge of electrical activity when the murderer was brought before it. Backster’s plants also displayed a strong aversion to interspecies violence. Some had a stressful response when an egg was cracked in their presence, or when live shrimp were dropped into boiling water, an experiment that Backster wrote up for the International Journal of Parapsychology, in 1968.”
While The Secret Life of Plants intrigued a generation or more of minds and hearts willing to change the standard view of plants being immobile, senseless vegetable matter, Pollan claims that the romanticism of the book may have damaged the reception of more recent ventures by plant scientists to more thoroughly explore the cognitive abilities of plants through controlled experiments that can be replicated. Some scientists go even further, claiming self-censorship, fearing that serious scientific studies of plant cognition will be poorly received. Nonetheless, there are scientists who label themselves “plant neurobiologists” who are working to radically transform our perceptions of our chlorophyll laden friends.
“The six authors—among them Eric D. Brenner, an American plant molecular biologist; Stefano Mancuso, an Italian plant physiologist; František Baluška, a Slovak cell biologist; and Elizabeth Van Volkenburgh, an American plant biologist—argued that the sophisticated behaviors observed in plants cannot at present be completely explained by familiar genetic and biochemical mechanisms. Plants are able to sense and optimally respond to so many environmental variables—light, water, gravity, temperature, soil structure, nutrients, toxins, microbes, herbivores, chemical signals from other plants—that there may exist some brainlike information-processing system to integrate the data and coördinate a plant’s behavioral response. The authors pointed out that electrical and chemical signalling systems have been identified in plants which are homologous to those found in the nervous systems of animals. They also noted that neurotransmitters such as serotonin, dopamine, and glutamate have been found in plants, though their role remains unclear.”
Michael Pollan actually traveled to Florence, Italy to meet Stefano Mancuso, who passionately pursues and defends the concept that having a vertebrate-type nervous system and being mobile are not necessary requirements for intelligence. He further explains that because plants are basically stuck where they are and are frequently consumed, their “modular” structures allow them to lose up to 90% of their bodily structures without dying. Because plants are literally rooted to the ground, their survival depends upon their ability to be highly aware of their surroundings and to use various modes of perception to defend and perpetuate themselves. Scientists claim that plants have as many as 15 to 20 senses to our 5, or 6, if you believe in intuition.
“Plants have evolved between fifteen and twenty distinct senses, including analogues of our five: smell and taste (they sense and respond to chemicals in the air or on their bodies); sight (they react differently to various wavelengths of light as well as to shadow); touch (a vine or a root “knows” when it encounters a solid object); and, it has been discovered, sound. In a recent experiment, Heidi Appel, a chemical ecologist at the University of Missouri, found that, when she played a recording of a caterpillar chomping a leaf for a plant that hadn’t been touched, the sound primed the plant’s genetic machinery to produce defense chemicals. Another experiment, done in Mancuso’s lab and not yet published, found that plant roots would seek out a buried pipe through which water was flowing even if the exterior of the pipe was dry, which suggested that plants somehow “hear” the sound of flowing water.”
If anything, reading this article will renew your sense of wonder and respect for the mostly silent green beings around us. Plants make up over 99% of the Earth’s biomass. Let’s hope they are not plotting to use their smarts to replace the insignificant 1%, of which we are only a small part!
Books about plant intelligence:
The Secret Life of Plants, by Peter Tompkins, 1973
The Secret Language of Life: how animals and plants feel and communicate, by Brian J. Ford, 2000
Brilliant Green: The Surprising History and Science of Plant Intelligence, by Stefano Mancuso
International Laboratory of Plant Neurobiology:
The New Scientist: Smarty Plants
Public Radio International article about plant intelligence: