How plants communicate with each other when in danger

By Kasha Patel October 21, 2023 at 7:00 a.m. EDT The Washington Post

(Illustration by Emily Sabens/The Washington Post; iStock)

It sounds like fiction from “The Lord of the Rings.” An enemy begins attacking a tree. The tree fends it off and sends out a warning message. Nearby trees set up their own defenses. The forest is saved.

But you don’t need a magical Ent from J.R.R. Tolkien’s world to conjure this scene. Real trees on our Earth can communicate and warn each other of danger — and a new study explains how.

The study found injured plants emit certain chemical compounds, which can infiltrate a healthy plant’s inner tissues and activate defenses from within its cells. A better understanding of this mechanism could allow scientists and farmers to help fortify plants against insect attacks or drought long before they happen.

The study marks the first time researchers have been able to “visualize plant-to-plant communication,” said Masatsugu Toyota, senior author of the study, which was published Tuesday in Nature Communications. “We can probably hijack this system to inform the entire plant to activate different stress responses against a future threat or environmental threats, such as drought.”

After a caterpillar devours a leaf, an Arabidopsis plant triggers calcium singling, as a long-distance wound signal propagates throughout the plant body and activates systemic defense responses (shown increasing here in green fluorescence). (Masatsugu Toyota/Toyota et al, Science 2018)

The idea of “talking” trees started to take root in the 1980s. Two ecologists placed hundreds of caterpillars and webworms on the branches of willow and alder trees to observe how the trees would respond. They found the attacked trees began producing chemicals that made their leaves unappetizing and indigestible to deter insects.

But even more curious, the scientists discovered healthy trees of the same species, located 30 or 40 meters away and with no root connections to the damaged trees, also put up the same chemical defenses to prepare against an insect invasion. Another pair of scientists around that time found similar results when studying damaged sugar maple and poplar trees.

These early research teams had a budding thought: The trees sent chemical signals to one another through the air, known today as plant eavesdropping. Over the past four decades, scientists have observed this cell-to-cell communication in more than 30 plant species, including lima bean, tobacco, tomato, sage brush and flowering plants in the mustard family. But no one knew which compounds were important and how they were being sensed — until now.

“There was this kind of controversy in the field,” said André Kessler, a plant ecologist who was not involved in the research. “First, how those compounds in general are taken up [by the plant], and then how they are able to change the plant’s metabolism in response to perceiving them.” (Continue to The Washington Post for the full article)