Plants Revealed 'Talking' to Each Other About Insects in Video

Go out into any garden, park or forest and you will be surrounded by a silent cacophony of conversations. Conversations between plants.

The fact that plants can "talk" has been known about for several decades. But how they can "hear" each other has remained largely unknown. Until now.

In a study published in the journal Nature Communications on October 17, researchers at Saitama University in Japan revealed in real time how plants receive communication signals from their neighbors, and how they can respond.

"Plants emit an array of [signaling] compounds in response to wounding and herbivore attacks," the study's lead author, Masatsugu Toyota, told Newsweek. "These [signaling compounds, known as] volatile organic compounds (VOCs) exert multiple protective effects, such as directly repelling herbivores and attracting natural enemies of the herbivores. Neighboring intact plants perceive these VOCs as danger cues to trigger defense responses or prime themselves to respond to upcoming stresses in a timely manner."

One specific group of these VOC signals—called green leaf volatiles—is released when plants are mechanically damaged or attacked by insects, to warn their neighbors of the upcoming threat. These molecules are also responsible for the smell of freshly cut grass (which is basically the smell of the grass plants screaming). But how do other plants detect and respond to these warning cues?

"Unlike animals, plants do not possess a 'nose,'" Toyota said.

To observe these responses firsthand, the team collected VOCs released from a group of plants fed on by caterpillars and pumped them onto undamaged neighboring plants. These neighboring plants had been engineered with a real-time fluorescence imaging system. This allowed the researchers to monitor the internal concentration of calcium ions inside the plants' cells. Calcium ions are known to play an important role in the signaling of stress responses inside plants so can be monitored to show the real-time transmission of a plant's stress response.

What they found was that these external cues are detected first by cells that line the tiny holes in a leaf's surface, called stomata, which allow air and water in and out of the plant. "In other words, the plant's stomata act as a gateway ('nose') to sense neighboring conditions," Toyota said. "These novel findings help understand the mechanisms of 'talking' plants."

As well as providing fascinating insights into the inner workings of our natural world, these results could pave the way to developing more effective pest controls in agriculture and global food production.

"Pesticides are extensively used for pest control all over the world, producing drug-resistant pests," Toyota said. "It might be possible to create a new airborne agricultural chemical (volatile) to protect crops and vegetables from pests by activating plants' intrinsic defense responses but not by killing pests."