By Katie L. Burke, award-winning editor and science journalist. She is an editor at American Scientist. Originally published on In darkness.
In 1973, the bestselling book “The Secret Life of Plants” was published, captivating audiences with questions about plant sentience and communication. Even if you haven’t read the book, you’ve probably heard of the experiments it describes: playing classical music and rock and roll on plants, for example, or hanging them on a polygraph. The book even inspired a movie with a soundtrack by Stevie Wonder.
The experiments were fun ideas, but poorly designed. Scientists have strongly rejected the book and distanced themselves from its views. “According to botanists working at the time, the damage Secret Life did to the field cannot be overestimated,” writes Zoë Schlanger in her new book “The Light Eaters: How the Invisible World of Plant Intelligence Offers New Understanding of Life on Earth.” “In subsequent years,” Schlanger reports, “the National Science Foundation became more reluctant to provide grants to anyone studying the responses of plants to their environments.” And, she continues, “scientists who had been pioneers in this field changed course or abandoned science altogether. »
It took about 40 years – a generation of scientists – for this deterrent effect to wear off. Over the past 15 years, funding for plant behavior research has resumed, at least in small amounts. Schlanger serves as a tour guide through this history and the pressing questions posed by new research about the shared future of plants and humans.
Given the history of research into plant intelligence, the book’s subtitle may raise skepticism. Even very popular books like “The Hidden Life of Trees” have been criticized for their get ahead evidence in plant communication. But “The Light Eaters” delivers on its promise: Schlanger’s thinking is rigorous, and she describes these controversial intellectual debates with a sense of fairness and curiosity.
There is obvious enthusiasm in Schlanger’s efforts to meet the few scientists who have been able to advance this field. His exploration takes him all over the world: to a Chilean rainforest to see a plant that imitates others like a chameleon; the Hawaiian island of Kaua’i, home to an impressive number of rare and endangered plants; and the University of Bonn in Germany, to meet one of the founders of the Society for Plant Neurobiology (now called the Society of Plant Signaling and Behavior). It hasn’t been easy for the scientists she meets along the way. Although a lucky, intrepid few have painstakingly carved out a niche for themselves, Schlanger encounters many who put their careers on the line to research the strange abilities of plants to perceive their world; some have unfortunately left the field completely. Others put their research on hold for decades, turning to teaching or more fundable research questions.
Despite the challenges on the ground, Schlanger finds a dynamism in her subject that stands in stark contrast to her work as a climate journalist, where she was beginning to burn out from all the grim news she dealt with on a daily basis. “Journalists in my line of work tend to focus on death. Or the warning signs: illness, disaster, decline,” she writes. She wanted to be around life, to celebrate it, as she rarely could in her daily work. “At a time when the planet is in ruins, plants provide a window into a green way of thinking,” she writes. The world’s flora “permeates our atmosphere with the oxygen we breathe, and it literally builds our bodies from the sugars it produces from sunlight,” she continues. “They have their own complex and dynamic lives – a social life, a sex life, and a whole host of subtle sensory appreciations that we generally assume are solely the domain of animals.”
“Understanding plants will open a new horizon of understanding for humans: we share our planet with and owe our lives to an inherently cunning life form, both alien and familiar. »
Indeed, Schlanger covers how plants perceive and respond to their environments – or the evidence that they possess such senses, even if scientists don’t know the underlying mechanisms. Plants communicate not only through chemicals in the air and soil, but also, potentially, through sound. Air bubbles burst when water flows from a plant’s roots to its stems, emitting an ultrasonic clicking sound. Each type of plant studied – wheat, corn, vines and cacti, for example – has a unique frequency. Plants can also perceive touch and transmit electrical signals, allowing them to communicate in other ways. And these beings perceive light in sophisticated ways that evoke comparisons to vision; A vine that grows in the Chilean rainforest, Boquila trifoliolata, can imitate neighboring plants down to the shape, texture and pattern of leaf veins, although no one yet knows how it can “see” its neighbors. Plants also have memory and social behaviors. A plant in the nettle family, Nasa Poissoniana, can anticipate when a pollinator will visit its star-shaped flowers, based on the time intervals passed between visits, and raise its pollen-bearing stamens.
However, plants do not have brains: their intelligence is not centralized, but rather a distributed network. “How is information about the world integrated, sorted by importance and translated into actions beneficial to the plant? » asks Schlanger. That’s the question at the forefront of research, and whether plants are conscious is an ongoing — and raging — debate. Schlanger seems sympathetic to neuroscientist Giulio Tononi’s idea that the complexity and integration of electrical wave patterns indicate an organism’s level of consciousness. From this point of view, consciousness is a spectrum and not a binary spectrum.
One of the pitfalls of using language to describe these phenomena is that it is almost impossible to avoid a certain level of anthropomorphization. Describing how botanists viewed the use of the word intelligence, Schlanger writes: “Measuring plants against human cognition made no sense; it simply transformed the plants into lower humans, lower animals. However, plants “deploy several senses – or could we say, intelligences? – which far exceeds anything humans can do in a similar category. Scientists have wrapped this information in “layers of blanket, language that keeps plants away from ourselves at all costs,” ultimately making it difficult for their work to reach the public or other disciplines. Schlanger argues that people need understandable metaphors – metaphors that they can connect to but that do not inform them about the difference between plants and humans. Or perhaps, she considers, we need to “vegetalize our language,” calling traits “plant memory,” “plant language,” or “plant feeling.”
A cabbage caterpillar eats a leaf of the Arabidopsis mustard, stimulating a surge of calcium through the plant that triggers defense responses in other leaves. Calcium is visualized by fluorescent light. Visual: Simon Gilroy/University of Wisconsin-Madison/YouTube
Schlanger explores why scientists have neglected such fundamental ideas about plants – even though many indigenous traditions treated them as relatives, ancestors, or simply beings in their own right. Schlanger covers not only these indigenous philosophies, but also how influences on European thought from Aristotle and René Descartes led to treating living things as mechanistic and passive. Although botanists use much livelier language in their conversations, they describe plant behaviors in their research papers using the passive voice. “A plant does not ‘react’, but ‘is affected’,” emphasizes Schlanger. “Articulating these processes without attributing an action to them is actually quite difficult, clumsy and imprecise. »
Recognize that plants are not simply passive, mechanistic groupings of cells, but rather intelligent beings, perhaps even worthy of personhood – meaning “each has free will, the will, and the right to exist for itself” – has enormous moral, philosophical and political implications. Several legal arguments have focused in recent years on the personality of plants and ecosystems threatened by human activities. “When do plants pass through the doors of our gaze? » asks Schlanger. “Is it when they have the tongue? When do they have family structures? When they make allies and enemies, have preferences, plan ahead? When we find out they can remember? They indeed seem to have all these characteristics. It is now up to us to choose whether or not we let this reality in.
Schlanger repeatedly exposes the yawning distance between the public and scientists when confronted with the question of plant intelligence. For example, Monica Gagliano, a plant researcher in Australia, has become a “contested figure” in her field for her strong stances on the study of plant hearing ability – and on the use of intuition as well as rigor based on evidence. “She speaks to large audiences at conferences on philosophy and at scientific events aimed at the general public,” writes Schlanger. At the same time, it is no longer funded by traditional federal grants, but by the Templeton World Charity Foundation.
Readers who loved “The Secret Life of Plants” may be disheartened to discover that the book harmed the very scientists they would have liked to help. “The greatest fault and greatest virtue of science is that it almost always confuses agreement with truth,” Schlanger writes. Questions about plant intelligence may even spark a spiritual and moral dilemma within science, a paradox that historian Jessica Riskin of Stanford University has explored. writing: “The 17th century banishment of action, perception, consciousness and will from nature and the natural sciences gave the monopoly of all these attributes to an external god.” Early scientists avoided these topics because this view of nature fit with the religious ideas of the time. “They bequeathed to their heirs a dilemma which remains relevant more than three centuries later. »
Recognizing the action of plants could rid science of this vestige of the past and, Schlanger bets, spark a new paradigm, one that integrates nature with humans and recognizes the action of all life. “Plants will remain plants no matter what we decide to think about them,” notes Schlanger. “But how we decide to view them could change everything for us.”
