Plants “Scream” While Being Harvested

St. Croix Times Staff

Scientists have captured the sound of plants “screaming” when harvested. The sound is not the same made by humans, but a popping or clicking noise in ultrasonic frequencies outside the range of human hearing. 

The sound increases when the plant becomes stressed, researchers from Tel Aviv University in Israel said in the study published in the scientific journal Cell. It added that this could be one of the ways that plants use to communicate their distress to the world around them. 

“Even in a quiet field, there are actually sounds that we don’t hear, and those sounds carry information. There are animals that can hear these sounds, so there is the possibility that a lot of acoustic interaction is occurring,” Lilach Hadany, Evolutionary Biologist at the University stated about the recent study. 

“Plants interact with insects and other animals all the time, and many of these organisms use sound for communication, so it would be very suboptimal for plants to not use sound at all,” she went on.

In incidents where plants are under stress, they undergo some dramatic changes one of them being emitting some powerful aromas. They can also change their color and shape.

To find out if plants produce sounds Ms. Hadany and her team recorded tomato and tobacco plants both in stressed and unstressed conditions. Their definition of distressed included plants that were having their stems cut or were dehydrated. 

The scientists then trained a machine learning algorithm to differentiate between the sounds produced by unstressed plants, cut plants, and dehydrated plants.  

The team found that the sound of distressed plants was far too high-pitched for humans to make out, and detectable within a radius of over a metre. However, it’s not yet clear how the plants produce the noises.

Stressed plants are much noisier, emitting an average up to 40 clicks per hour depending on the species. And plants deprived of water have a noticeable sound profile. They start clicking more before they show visible signs of dehydrating, escalating as the plant grows more parched, before subsiding as the plant withers away.  

Meanwhile, they found that unstressed plants don’t make much noise at all, they just hang out and quietly do their plant thing.

The findings shatter the common perception of plants as silent, passive background players to the animal life in their environments.

“Now that we know that plants do emit sounds, the next question is - who might be listening?” Ms. Hadany wondered.