Plants Have Feelings and Can Sense Pain

A Group of Scientists Suggest that Plants Feel Pain

For years, scientists are baffled by the question of whether plants can feel pain or not. A team of scientists from Tel Aviv University may have the answer to that question, as they discovered that some plants can emit a high-frequency distress sound when in environmental stress. 

The team of researchers tested tobacco plants and tomato plants by not watering them and by cutting off their stems. They then recorded their response with a microphone that was placed ten centimeters away. 

In both cases, the scientists found that the plants began to emit ultrasonic sounds that were between 20 and 100 kilohertz, which they believed could convey their distress to other organisms and plants within the vicinity. When the stem of a tomato plant was cut, the researches found it emitted 25 ultrasonic distress sounds over the course of an hour, according to the study that was published in Live Science.

The tobacco plants that had its 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 plants also seemed to respond with the different intensities of sound to different sources of environmental stress. They observed that the tobacco plants let out louder sound when they were not watered than when they had their stems cut.

The plants that did not experience any environmental stress, damage, or threat released less than one ultrasonic sound per hour.

Do plants feel pain?

The group 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 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.

Last year, another study found that some plants registered pain after their leaves were touched and plucked, which eventually caused the release of foul-tasting chemicals across the leaves. It is believed that the chemical is released to ward off insects.

Response to environmental stress

The smell that we usually associate with freshly cut grass is actually a chemical distress call. It is used by plants to beg critters to save them from attack. To protect themselves, plants employ numerous molecular responses. These chemical communications can be used to poison an enemy, alert the surrounding plants to potential dangers, or attract helpful insects to perform needed services.

Clearly, plants can communicate. But does that mean they can feel pain? It's a troubling scenario for salad lovers squeamish at the thought of eating foods with feelings, and for them the answer may not be that appetizing.

There is also evidence that plants can hear themselves being eaten. A group of researchers at the University of Missouri-Columbia found that plants can understand and respond to the chewing sounds that are made by caterpillars while they are eating them. As soon as the plants hear the noises, they automatically respond with numerous defense mechanisms.

According to researchers at the Institute for Applied Physics at the University of Bonn in Germany, plants release gases that are the equivalent of crying out in pain. Using a laser-powered microphone, researchers have picked up sound waves produced by plants releasing gases when cut or injured. Although not audible to the human ear, the secret voices of plants have revealed that cucumbers scream when they are sick, and flowers whine when their leaves are cut.

As they grow, plants can alter their trajectories to avoid obstacles or reach for support with their tendrils. This activity stems from a complex biological network distributed through the plants' roots, leaves and stems. This network helps plants propagate, grow and survive. Trees in a forest, for instance, can warn their relatives of insect attacks.

One scientist injected fir trees with radioactive carbon isotopes and saw that within a few days the carbon had been sent from tree to tree until every tree in the 30-meter-square area was connected. The scientist learned that the mature trees "communicated" to the network to share nutrients through their root systems to feed nearby seedlings until they were tall enough to take in light for themselves.

Main Sources:

https://www.sciencetimes.com/articles/24473/20191218/a-group-of-scientists-suggest-that-plants-feel-pain.htm

https://science.howstuffworks.com/life/botany/plants-feel-pain.htm

Supplementary Information:

http://www.bbc.com/earth/story/20170109-plants-can-see-hear-and-smell-and-respond

https://www.britannica.com/story/do-plants-feel-pain

https://www.theguardian.com/environment/shortcuts/2020/nov/23/sensitive-flower-do-plants-really-have-personalities