The Intelligent Plant

Scientists debate a new way of understanding flora

This excerpt is from a story by Michael Pollan (Omnivore’s Dilemma, Botany of Desire) published Dec. 23, 2013 in The New Yorker

Studies done at Sagehen Creek Field Station show that Artemisia tridentata sagebrush warn relatives of danger when their leaves are clipped. Plants receiving the chemical messages amp up their production of volatile compounds that ward off insect pests. Image credit: Kathleen M. Wong
Studies at Sagehen Creek Field Station show that Artemisia tridentata sagebrush use chemical messages to warn relatives of danger from insect pests. Image credit: Kathleen M. Wong

Plants speak in a chemical vocabulary we can’t directly perceive or comprehend. The first important discoveries in plant communication were made in the lab in the nineteen-eighties, by isolating plants and their chemical emissions in Plexiglas chambers, but Rick Karban, the U.C. Davis ecologist, and others have set themselves the messier task of studying how plants exchange chemical signals outdoors, in a natural setting. Recently, I visited Karban’s study plot at the University of California’s Sagehen Creek Field Station, a few miles outside Truckee. On a sun-flooded hillside high in the Sierras, he introduced me to the ninety-nine sagebrush plants—low, slow-growing gray-green shrubs marked with plastic flags—that he and his colleagues have kept under close surveillance for more than a decade.

Karban, a fifty-nine-year-old former New Yorker, is slender, with a thatch of white curls barely contained by a floppy hat. He has shown that when sagebrush leaves are clipped in the spring—simulating an insect attack that triggers the release of volatile chemicals—both the clipped plant and its unclipped neighbors suffer significantly less insect damage over the season. Karban believes that the plant is alerting all its leaves to the presence of a pest, but its neighbors pick up the signal, too, and gird themselves against attack. “We think the sagebrush are basically eavesdropping on one another,” Karban said. He found that the more closely related the plants the more likely they are to respond to the chemical signal, suggesting that plants may display a form of kin recognition. Helping out your relatives is a good way to improve the odds that your genes will survive.

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To read this story in its entirety, see The New Yorker