https://www.scientificamerican.com/article/sweet-potato-sends-secret-signals/

When nibbled, the leaves of one type of sweet potato release a strong-smelling chemical warning that prompts other leaves—on the same plant and those nearby—to produce defensive proteins that make them hard to digest. New research tracks this odorous alert system.

“It’s sort of a shortcut,” says Axel Mithöfer, a plant ecologist at the Max Planck Institute for Chemical Ecology in Jena, Germany, and co-author of the study, which appeared last November in Scientific Reports. Other plants have chemical warning systems that prompt neighbors to prepare for attack, but individual leaves often wait to manufacture defensive compounds until bitten themselves. But this plant’s leaves produce the compound immediately when neighbors are bitten, he says.