Plants can make noises when under stress, study says

FILE - Stock shot of tomatoes on the plant in a local hot house. (Michael Bradley/Getty Images)

Mum is not the word because apparently plants make noises, according to researchers from the University of Tel Aviv in Israel. 

A recent study found that some plants actually make noises when they are put under stress. 

Researchers were able to record ultrasonic sound ranges of different plants and depending on what type of threat or stress the plant was under, the sounds came out differently, according to the study published in the journal Cell. 

Tomato plants and tobacco plants were the focus of the experiment but wheat, corn, cactus and henbit were also recorded. 

When a plant was cut or dehydrated, the sounds it emitted were far louder than when they were properly watered and left alone. 

The noises from the plants resembled that of popping popcorn. 

"Our recordings indicated that the plants in our experiment emitted sounds at frequencies of 40-80 kilohertz. Unstressed plants emitted less than one sound per hour, on average, while the stressed plants – both dehydrated and injured – emitted dozens of sounds every hour," researchers said in a statement. 

The study noted that the sound frequency the stressed plants emitted can actually be heard by mammals and insects from a distance of 3 to 5 meters. The frequency is too high, however, for humans to hear it.

"In this study we resolved a very old scientific controversy: we proved that plants do emit sounds!" said Prof. Lilach Hadany, the study lead. "Our findings suggest that the world around us is full of plant sounds, and that these sounds contain information – for example about water scarcity or injury. We assume that in nature the sounds emitted by plants are detected by creatures nearby, such as bats, rodents, various insects, and possibly also other plants - that can hear the high frequencies and derive relevant information. We believe that humans can also utilize this information, given the right tools - such as sensors that tell growers when plants need watering. Apparently, an idyllic field of flowers can be a rather noisy place. It's just that we can't hear the sounds."

Researchers now hope to continue these sorts of studies such as how the plants make sounds, how insects react to these sounds and can other plants hear other plants? 

This story was reported from Los Angeles.