It turns out almost every green plant that’s been studied releases its own cocktail of volatile chemicals, and many species register and respond to these plumes. For example, the smell of cut grass — a blend of alcohols, aldehydes, ketones and esters — may be pleasant to us but to plants signals danger on the way. [Martin] Heil has found that when wild-growing lima beans are exposed to volatiles from other lima bean plants being eaten by beetles, they grow faster and resist attack. Compounds released from damaged plants prime the defenses of corn seedlings, so that they later mount a more effective counterattack against beet armyworms. These signals seem to be a universal language: sagebrush induces responses in tobacco; chili peppers and lima beans respond to cucumber emissions, too.
University of Missouri Professor Jack Schulz discusses a mechanical nose he is developing that might help farmers understand and even respond to these plant signals:
One day, farmers might not just be able to eavesdrop in on their crops’ airborne anxieties. They might even be able to whisper back. The idea comes from Professor Jack Schultz at the University of Missouri, who earned a brief mention in Michael Pollan’s amazing article on plant intelligence in the New Yorker. Schultz, a chemical ecologist, pioneered some of the first studies of plant communication in the 1980s. He is now working to develop a mechanical nose a farmer could use to pick up the chemical alarm bells of a crop under attack. If it works (which remains an if) farmers could apply pesticides with a high degree of precision. …
Gaining a richer picture of plant conversations takes an extremely precise nose, which humans lack, but dogs have. Vineyards in California contract dog trainers to search out invasive mealy worms. “So if you could duplicate a dog’s nose,” says Schultz, “you could see the world of chemical signalling. Us humans just aren’t attuned to that.” Other animals know bits and pieces of plant language, which is exactly why the plants might put out the signals in the first place. When a caterpillar starts munching on a corn crop, Schultz has found, the plant releases a beacon for wasps to take care of the problem.
The Dish 