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A New Book About Plant Intelligence Highlights the Messiness of Scientific Change

The New Yorker [unpaywalled], In “The Light Eaters,” by Zoë Schlanger the field of botany itself functions as a character—one in the process of undergoing a potentially radical transformation: “During the nineteen-seventies and eighties, a researcher at the University of Washington started noticing something strange in the college’s experimental forest. For years, a blight of caterpillars had been munching the trees to death. Then, suddenly, the caterpillars themselves started dying off. The forest was able to recover. But what had happened to the caterpillars? The researcher, David Rhoades, who had a background in chemistry and zoology, found that the trees in the forest had changed the chemistry of their leaves, to the detriment of the caterpillars. Even more surprising, trees that had been nibbled by caterpillars weren’t the only ones that had changed their chemistry. Some were changing their leaves before caterpillars reached them, as if they’d received a warning. A shocking possibility presented itself: the trees were signalling to one another. Zoë Schlanger recounts Rhoades’s story in her new book, “The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth.” In a research paper that Rhoades published on his findings in the Journal of the American Chemical Society’s series “Plant Resistance to Insects,” he pointed out that the trees were too far apart to be communicating through their roots. This suggested a possibility so novel that Rhoades couldn’t resist an exclamation point in his otherwise cautious positing—the trees seemed to be using “airborne pheromonal substances!” That paper, Schlanger writes, “would change everything, and in a cruel twist, it would end his career. Because back then, no one believed him.” The contemporary world of botany that Schlanger explores in “The Light Eaters” is still divided over the matter of how plants sense the world and whether they can be said to communicate. But, in the past twenty years, the idea that plants communicate has gained broader acceptance. Research in recent decades has shown garden-variety lima beans protecting themselves by synthesizing and releasing chemicals to summon the predators of the insects that eat them; lab-grown pea shoots navigating mazes and responding to the sound of running water; and a chameleonic vine in the jungles of Chile mimicking the shape and color of nearby plants by a mechanism that’s not yet understood…”

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