Plants can sense the pheromones of nematode worms

ITHACA, N.Y., July 24 (UPI) -- New research suggests some plants can sense, or "smell," the chemical signatures of encroaching leaf-munchers.

The proverbial game of cat and mouse -- the never-ending arms race between hunters and the hunted -- is played by all creatures, not just felines and rodents. As a new study demonstrates, even plants participate.

Plants can "see" and grow toward light. And previous studies have shown plants can "hear" the vibrations of munching caterpillars. Now, new research by scientists at Cornell University suggests plants can pick out the scent of parasitic roundworms and other harmful nematodes.

Researchers already knew that plants can sense chemicals via their roots. To see if they could pick up the chemical signatures of underground predators, researchers began analyzing the pheromones, or ascarosides, given off by several species of parasitic nematodes.

Each nematode species may use dozens of ascarosides as a primitive form of communication. In their research, scientists identified one ascaroside, called ascr#18, common to many different nematode species.

When researchers exposed the roots of tomato, potato, barley and lab-bred thale cress plants to water spiked with a trace amount of ascr#18, they observed an uptick in each plant's chemical defenses. Plants exposed to the key ascaroside prior to being exposed to a barrage of pests suffered less damage to their leaves.

The ascaroside triggered the plants' immune systems to pump out chemical defenses, effective not just against nematodes but against bacterial, fungal and viral pathogens, too.

"When a class of parasites has made the same compounds for millions of years, then their hosts may learn how to detect those molecules." Frank C. Schroeder, a professor at Cornell's Boyce Thompson Institute for Plant Research, explained in a press release. "This apparently has happened with plants, which have likely been under nematode attack for several hundred million years."

Schroeder is one of the authors of a new study on the subject, published this week in the journal Nature Communications. He and his colleagues hope their discovery will help researchers create less toxic pesticides.

"We show that plants have learned to perceive nematodes, and in response to that, they get stronger. They turn on pathways that help them fend off disease," said Schroeder. "Therefore, the use of ascr#18 may have great potential in agricultural applications for broad-spectrum protection."