Do Plants Feel Pain? What We Know About Plants’ ‘Distress Signal’

Plants are often considered to be silent and passive organisms that merely react to their environment.

However, recent research has revealed that plants are capable of complex signaling and communication systems that allow them to sense and respond to various stimuli, including potential threats.

In this article, we will explore the fascinating question of whether plants feel pain, and how they use chemical and acoustic signals to convey their distress and defend themselves.

How Plants Sense and Respond to Stress

(Photo : GUILLAUME SOUVANT/AFP via Getty Images)

Pain perception is typically associated with living organisms that possess a nervous system, which includes specialized sensory receptors, neurons and regions of the brain responsible for processing sensory information.

Plants do not have a brain or nervous system, but they do exhibit intricate biochemical pathways and plant-signaling molecules like hormones that enable them to adapt to their environment.

Plants use a variety of chemical and electrical signals to sense changes in light, gravity, temperature and touch.

They can also respond to external stimuli by growing toward or away from them, adjusting their root and shoot growth and producing defense compounds against predators.

These responses are managed by a complex biological network that coordinates the activities of different cells and tissues.

One of the most remarkable examples of plant signaling is the release of volatile organic compounds (VOCs) that can serve multiple functions.

VOCs are airborne molecules that can travel over long distances and affect the behavior of other organisms.

For instance, plants can use VOCs to attract pollinators, repel herbivores, poison enemies, recruit allies, warn neighboring plants or even communicate with themselves.

The smell we associate with freshly cut grass is actually a chemical distress call, one used by plants to beg nearby critters to save them from attack (usually it's an affront by insects, but in this case, it's lawnmower blades). This defense response beckons the question: Do plants feel pain?

Also Read: Fish Do Not Feel Pain, Say Scientists

How Plants Emit Ultrasonic Sounds When in Distress

The answer to whether plants feel pain is not straightforward, as they do not feel pain like us humans do, but some plant scientists posit that they may feel pain in their own way.

One of the most intriguing evidence for this hypothesis is the discovery that some plants can emit ultrasonic sounds when they experience environmental stress.

A team of scientists from Tel Aviv University found that tobacco plants and tomato plants can produce high-frequency distress sounds that are between 20 and 100 kilohertz, which they believed could convey their distress to other organisms and plants within the vicinity.

The researchers tested the plants by not watering them and by cutting off their stems. They then recorded their response with a microphone that was placed 10 centimeters away.

In both cases, the scientists found that the plants began to emit ultrasonic sounds that varied in intensity and frequency depending on the type and severity of the stress.

When the stem of a tomato plant was cut, the researches found it emitted 25 ultrasonic distress sounds over the course of an hour. The tobacco plants that had their stem cut sent out 15 distress sounds.

When the team of scientists deprived each plant of water, the tomato plants emitted even more distress sounds, increasing to 35 in one hour, while the tobacco plants made 11.

The team of scientists wrote in their paper that these findings can alter the way that we think about the plant kingdom, which has been considered to be almost silent and not given much thought.

The researchers used the data that they had gathered in a machine learning model to be able to predict the different frequency of sound that plants may emit under other conditions like heavy rain or wind.

The team scientists believe that listening to the different types of sounds that are emitted by plants could help with precision agriculture, and it can allow farmers to identify any potential issue with their crops.

Related article: Plants May Be Able to See, Scientists Discover