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Plants can sense when they're being touched, according to a new study

The Washington State University-led study included a team of international researchers.

PULLMAN, Wash. — A study out of Washington State University found plants can sense when they're being touched, even though they don't have nerves.

One scientist heading up the study says the new findings are just the beginning of more discoveries down the road.

“If you look at plants outside, usually you don't see a lot of movement or dynamics. This is very different when you look at a cellular level with a microscope,” said Michael Knoblauch, a WSU professor of plant cell biology and senior author of the study.

A video from the study shows a slow wave of light emanating from the point where the plant has been touched.

“Basically what the cell does is telling the neighboring cells, ‘I have been touched',” explained Knoblauch.

Over the course of four years, an international team of scientists conducted more than 80 experiments using 12 plants. They put the plants under a microscope, then slightly touched the plant's skin with a tiny glass rod, about the size of a human hair.

Not only did the plant respond with a slow wave of calcium ions, an essential plant nutrient, but once it was no longer being touched, Knoblauch said the plant began sending different signals that moved faster in different patterns. In order for researchers to see the wave of calcium ions, the plants in the study were specially bred to include calcium sensors.

The study’s authors think the waves are related to the change in pressure inside the plant cells. The idea is that plants cells have strong walls, so when they’re touched, pressure increases inside the plant cells.

He said this ability to sense touch could be part of a defense mechanism.

“Plants have absolute measures to defend themselves, if for example you cut roses, the next rose stick that comes out has way more thorns than the previous one,” Knoblauch said.

But scientists still need to figure out how those defenses work. It's information that could be particularly useful in the agricultural industry.

“If we understand how plants protect themselves, we potentially can trigger it and instead of using chemicals, we could use a trigger to make them protect themselves against aphids, against other pests,” said Knoblauch.

These recent discoveries are now being added to the foundation of what we know about plants, that'll help spur future innovation.

“Right now it's up for imagination,” Knoblauch said.

He said for a few decades now, we've known touch can trigger a response in plants.

For instance, a caterpillar munching on a leaf can trigger other parts of the same plant to start producing chemicals that make it less tasty or even toxic to the animal eating it.

Now, scientists will try to get a better handle on how it all works.

A grant from the National Science Foundation helped pay for the study. The international team included researchers from the Technical University of Denmark, Ludwig Maximilian Universitaet Muenchen and Westfaelische Wilhelms-Universitaet Muenster in Germany, University of Wisconsin-Madison, as well as Washington State University.

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