The Big Picture
The Intelligence of Plants
By Cody DelistratyWhat if plants are smarter than we think—a lot smarter?
Miguel Rio Branco, Untitled, Tokyo, 2008 © Miguel Rio Branco
A few years ago, Monica Gagliano, an associate professor in evolutionary ecology at the University of Western Australia, began dropping potted Mimosa pudicas. She used a sliding steel rail that guided them to six inches above a cushioned surface, then let them fall. The plant, which is leafy and green with pink-purple flower heads, is commonly known as a “shameplant” or a “touch-me-not” because its leaves fold inward when it’s disturbed. In theory, it would defend itself against any attack, indiscriminately perceiving any touch or drop as an offense and closing itself up.
The first time Gagliano dropped the plants—fifty-six of them—from the measured height, they responded as expected. But after several more drops, fewer of them closed. She dropped each of them sixty times, in five-second intervals. Eventually, all of them stopped closing. She continued like this for twenty-eight days, but none of them ever closed up again. It was only when she bothered them differently—such as by grabbing them—that they reverted to their usual defense mechanism.
Gagliano concluded, in a study published in a 2014 edition of Oecologia, that the shameplants had “remembered” that their being dropped from such a low height wasn’t actually a danger and realized they didn’t need to defend themselves. She believed that her experiment helped prove that “brains and neurons are a sophisticated solution but not a necessary requirement for learning.” The plants, she reasoned, were learning. The plants, she believed, were remembering. Bees, for instance, forget what they’ve learned after just a few days. These shameplants had remembered for nearly a month.
