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Plants Know When They’re Being Touched

Researchers saw a change in thousands of plant genes occurred just minutes after they were sprayed with water.
Image: Underside of Taro leaf via Wikimedia Commons.

Humans have been attributing a secret, interior life to plants for thousands of years. It began with the nature worship of our far-distant ancestors and continued on into the modern age thanks to people like Cleve Backster, a CIA polygraph expert who performed experiments in the 1960s to demonstrate that plants could read our minds.

By and large, most research seeking to attribute a mental life to plants has been discredited over the years. Yet new research coming out of the University of Western Australia shows that while plants may not be able to think, they are—in a way—able to feel.

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The UWA researchers arrived at this conclusion after they noticed that a change in the expression of thousands of plant genes occurred just minutes after they were sprayed with water. These genetic changes were short-lived (most reverted to their normal state within half an hour), suggesting that plants are highly in touch with their immediate environment and capable of dynamic responses to changes in their surroundings.

"Unlike animals, plants are unable to run away from harmful conditions," said Olivier Van Aken, the lead researcher in the study. "Instead, plants appear to have developed intricate stress defense systems to sense their environment and help them detect danger and respond appropriately.

According to the team, similar reactions in the plants were evoked when the researchers gently touched the plants, prodded them with tweezers, or cast a shadow over them. In nature, these defense responses in the plants could be triggered by rain drops falling on leaves, an insect walking over the plant, or even the wind blowing.

After determining that there weren't any active compounds in the spray that were triggering these responses in the plants, Van Aken and his team were able to identify two key proteins (AtWRKY15 and AtWRKY40) which turn on and off the plants' touch response.

"Switching off the response signal is very important," said Van Aken. "It allows plants to get on with life as normal, forgetting about the signal and treating it as a false alarm."

Ultimately, Van Aken thinks that the research will help shape the way humans interact with plants.

"Although people generally assume plants don't feel when they are being touched, this shows that they are actually very sensitive to it," he said. "While plants don't appear to complain when we pinch a flower, step on them or just brush by them while going for a walk, they are fully aware of this contact and are rapidly responding to our treatment of them."