Groundbreaking research finds that plants are not silent and they make popping sounds

According to a new study conducted by Cell, plants make popping sounds that cannot be heard by the human ear. The study also revealed they make other sounds when thirsty or under any form of stress. It is pioneering research and changes a lot that Botanists had known about the plant kingdom. Till now, plants were considered largely silent and this suggests the world around us is a "cacophony of plant sounds", said study co-author Lilach Hadany, reported CNN. Hadany added she had been skeptical for a long time about the complete noiselessness of plants.

“There are so many organisms that respond to sound, I thought there was no good reason for plants to be deaf and mute,” said Hadany, a professor at the School of Plant Sciences and Food Security and program head of the George S. Wise Faculty of Life Sciences at Tel Aviv University. The first plant Hadany had recorded, involving using an ultrasonic microphone, was a cactus in her lab six years ago, but she could not prove that the sound she detected was made by something else in the environment.

Moreover, previous studies have revealed that plants made vibrations, but it was not known whether these vibrations were airborne sound waves. To figure out whether plants actually were making sounds, Hadany and her team made use of soundproofed acoustic boxes. The researchers stored tobacco and tomato plants in boxes, rigged with ultrasonic microphones that record at frequencies between 20 and 250 kilohertz. According to science, the maximum frequency a human adult’s naked ear can detect is about 16 kilohertz. Some plants had cut stems or had not been watered for five days, while others were untouched.

The team discovered that the plants emitted sounds at a frequency of 40 to 80 kilohertz, and when condensed and translated into a frequency humans can hear, the noises could be compared to the pop of popcorn being made or bubble wrap bursting. A stressed plant emitted around 30 to 50 of these popcorn-like sounds per hour at random intervals, but unstressed plants emitted far fewer sounds in the same hour. “When tomatoes are not stressed at all, they are very quiet,” Hadany said.

“This result adds to what we know about plant responses to stress. It is a useful contribution to the field and to our general appreciation that plants are responsive organisms capable of sophisticated behaviors,” said Richard Karban, a distinguished professor of entomology at the University of California, Davis, who studies interactions between herbivores and their host plants. However, he was not part of this research.

“However, it should not be interpreted as showing that plants are actively communicating by making sounds,” Karban clarified.  Ecologist Daniel Robert said via an email, “Lots of sounds in the world are generated that are not ‘intentional’ signals, but nonetheless can be heard and used by other organisms for their own benefits. So, the concept of communication is indeed a challenge … does it need to be bi-directional to work and be considered as such?”

“The finding that there is information in the acoustic emissions, using neural network classification, is exciting as such (a) technique is fast and can identify data structures that the human eyes or ears cannot,” Robert further noted.

While Hadany said she now looked at plants and flowers differently. “There are many songs we can’t hear.” 

Indeed, there are so many songs we cannot hear, but now we know they exist. All thanks to Science!