Why It Matters | Plants emit ultrasonic sounds when distressed

Researchers have found that plants emit ultrasonic sounds when distressed.

Updated - April 04, 2023 08:42 am IST

Published - April 03, 2023 04:15 pm IST

Corn grows in a field outside Wyanet, Illinois, U.S., July 6, 2018.

Corn grows in a field outside Wyanet, Illinois, U.S., July 6, 2018. | Photo Credit: Reuters

What are the facts? Plants can emit sounds that are beyond the hearing range of humans, new research has shown. These sounds, recorded and analysed by researchers at Tel Aviv University, can provide a plethora of information, particularly when it is stressed or injured. The ultrasonic sound recorded by the researchers is a click-like sound (like the popping of popcorn) at a volume similar to human speech but at much higher frequencies of 40-80 kilohertz. The study, published in the journal Cell, also noted that unstressed plants emitted less than one sound per hour, however, stressed or injured plants emitted at least a dozen of sounds every hour.

What is the context?

  • The researchers primarily tested tomato and tobacco plants, however, sounds from wheat, corn, cactus and henbit were also recorded. The plants were subjected to a number of treatments such as some plants were not watered for five days, some had their stems cut while some were left untouched. 
  • The recordings were processed through a specially developed machine learning algorithm which could differentiate between plant species and the type of sounds being produced even when the plants were placed in a greenhouse among a lot of background noise. 
  • While there have been earlier studies on how plants communicate with each other using electrical signalling, volatile organic compounds and mycorrhizal networks between plants and other organisms, the current study is the first to show evidence of airborne soundwaves that can be recorded from a distance. 

Why does it matter?

  • The sounds emitted by plants can provide valuable information about their condition. “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,” said Professor Lilacch Hadany, the author of the study, in a release.
  • Researchers also assume that the ‘squeals’ of the plants can be heard by other animals who can hear at high frequencies such as bats, insects and possibly other plants and derive necessary information.
  • Though plants do not have brains or a central nervous system to feel ‘pain’ as humans or animals do, the current research adds to a growing number of studies that suggests that plants have evolved to avoid or respond to unpleasant stimuli that could cause them damage.

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