The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth

by Zoë Schlanger

Their work was based on earlier studies, in which scientists measured electrical impulses in the giant cells of Chara algae, a common pond weed. The Chara cells were enormous, as cells go—ten centimeters long, and a millimeter in diameter—and thus conveniently visible to the naked eye. You could jab an electrode right into one. And they were excitable in much the same way as human cells were. It took a long time for science to begin to ask plants more electrical questions. In 1992, a group of researchers from the UK and New Zealand found that they could block the chemical signaling in tomato seedlings, but that the plants would still accumulate the defensive proteins when another part of the plant was wounded. But they also noted that when a seedling was intentionally wounded, a flurry of electrical activity was detectable. Could the defensive signal be sent by way of electrical impulses, they wondered, instead of chemical ones? In a letter published in Nature, the researchers even went so far as to say that the electrical activity had “similarities to the epithelial conduction system used to transmit a stimulus in the defense responses of some lower animals.” In epithelial conduction, an electric signal is transported cell-to-cell, by way of narrow channels that let ions pass between adjacent cells. “Although plants lack any structures comparable to animal nerves,” they wrote, cells in a plant tissue are linked by narrow threads that have “electrical conductivities nearly...