PLANTS listen out for the sound of dripping water when they're thirsty, scientists have discovered.

They can sense water in a flowing pipe - or even a buzzing insect - by detecting the vibrations the water makes, experts claim.

2 Biologists found that pea roots could sense water even if it was hidden behind plastic Credit: Getty Images

There has long been a question mark over how plants tend to toward water sources.

Evolutionary biologist Monica Gagliano and her colleagues decided to get the bottom of it.

They placed pea seedlings into Y-shaped pots to test their hypothesis that plants might be able to sense liquid.

2 Beware, those leafy green vegetables might be listening in.. sort of Credit: Getty Images

One arm of each pot was placed in either a tray of water or a coiled plastic tube through which water flowed.

The other arm was placed in a tray of soil.

All roots grew toward the arm which had fluid - regardless of whether it was hidden by the plastic or free-flowing.

"They just knew the water was there, even if the only thing to detect was the sound of it flowing inside the pipe,” Gagliano said.

"Because water is essential to life, organisms have evolved a wide range of strategies to cope with water limitations, including actively searching for their preferred moisture levels to avoid dehydration.

"Plants use moisture gradients to direct their roots through the soil once a water source is detected, but how they first detect the source is unknown.

How did scientists discover plants could 'hear'? A group of biologists tested the hypothesis that plants could hear by placing pea seedlings into Y-shaped pots.

One arm of each pot was placed in either a tray of water or a coiled plastic tube through which water flowed.

The other arm was placed in a tray of soil.

They found that roots grew toward the arm which had fluid - regardless of whether it was hidden by the plastic or not.

"We found that roots were able to locate a water source by sensing the vibrations generated by water moving inside pipes, even in the absence of substrate moisture."

Vegetarians often turn to plant-based diets because they fear killing sentient beings.

But another recent plant study might make them think twice.

It turns out that they can tell when you're eating them.

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