Groundbreaking Study Finds Plants Emit Sounds When Stressed

Plants are often considered silent creatures, rooted to the ground and immobile. However, a groundbreaking study has recently found that plants emit sounds when stressed, challenging how we think about these seemingly passive organisms.

The study, published in the journal Trends in Plant Science, was conducted by a team of researchers from Tel Aviv University in Israel.

The researchers used advanced technology to record and analyze the sounds emitted by plants under various stress conditions, such as drought, heat, and physical damage.

Like popcorn popping, the sounds produced are audible at a level comparable to human speech. However, they are emitted at elevated frequencies outside the range of human auditory perception.

What the Researchers Found

According to their findings, when plants are experiencing stress, they typically produce sounds unique to the specific type and the type of stress it is undergoing. Although these sounds may be inaudible to humans, various animals, including bats, mice, and insects, can likely detect them.

Stressed plants emit sounds that can be heard by animals, new study finds https://t.co/on365PaCsU

— Sky News (@SkyNews) March 31, 2023

Prof. Lilach Hadany from the Wise Faculty of Life Sciences, School of Plant Sciences and Food Security, along with Prof. Yossi Yovel, the Head of the Sagol School of Neuroscience and a faculty member at the School of Zoology, led the study.

The researchers found that different types of stress produce various kinds of sounds. For example, drought-stressed plants emit sounds distinct from those emitted by plants subjected to physical damage. The researchers also found that plants emit sounds in response to certain chemicals, such as those released by herbivores.

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According to Professor Hadany, “Previous research has shown that vibrometers attached to plants can detect vibrations. However, there has been a long-standing debate among researchers regarding whether these vibrations also generate airborne sound waves that are recordable from a distance. Our study aimed to investigate this question.”

In the initial research phase, the scientists placed tomato, tobacco, wheat, corn, cactus, and henbit plants in a soundproof box in a quiet basement without background noise.

Ultrasonic microphones are capable of capturing sounds at frequencies ranging from 20 to 250 kilohertz, which are beyond the range of human hearing (the upper limit for human adults is approximately 16 kilohertz). They have been positioned about 10 cm away from each plant.

Plants emit ultrasonic sounds in rapid bursts when stressed, scientists say https://t.co/lNNPxsmfka

— The Guardian (@guardian) March 30, 2023

The Study and its Implications

The experiment aimed to determine whether plants emit sounds and whether their condition affects the sounds they produce. To achieve this goal, the researchers subjected some plants to various treatments, such as withholding water for five days or cutting the stem, while they didn’t touch the others.

The results of the recordings showed that the plants emitted sounds in the frequency range of 40 to 80 kilohertz. The average number of sounds that non-stressed emit was less than one per hour, while stressed plants, whether dehydrated or injured, emitted dozens of sounds per hour.

The researchers then analyzed the recorded sounds using machine learning algorithms developed for this purpose. The algorithms can differentiate between different types of flora and sounds. They can also identify the specific plant and the level and type of stress from the recordings.

How the algorithms work

Furthermore, the algorithms successfully classified plant sounds even in a noisy greenhouse environment. In the greenhouse, the researchers monitored dry plants over time. They observed an increase in the number of sounds emitted. Until a certain peak, after which the number of sounds diminished.

Professor Hadany stated that the study has finally resolved a long-standing scientific debate, confirming that plants emit sounds. The research suggests that the environment contains plant sounds. This can collect crucial information such as water scarcity or damage.

The implications of this study are significant. For one, it challenges the idea that they are passive organisms that react to their environment. Instead, it suggests that plants actively communicate with their surroundings, alerting other flora and animals to potential danger.

“We believe that humans can also use this information, given the proper tools – such as sensors that alert growers when plants need watering. A field of flowers can be a really noisy place. It’s just that we cannot hear the sounds,” Prof. Hadany explained.