[www.biorxiv.org]

Abstract


Stressed plants show altered phenotypes, including changes in color, smell, and shape. Yet, the possibility that plants emit airborne sounds when stressed – similarly to many animals – has not been investigated. Here we show, to our knowledge for the first time, that stressed plants emit airborne sounds that can be recorded remotely, both in acoustic chambers and in greenhouses. We recorded ?65 dBSPL ultrasonic sounds 10 cm from tomato and tobacco plants, implying that these sounds could be detected by some organisms from up to several meters away. We developed machine learning models that were capable of distinguishing between plant sounds and general noises, and identifying the condition of the plants – dry, cut, or intact – based solely on the emitted sounds. Our results suggest that animals, humans, and possibly even other plants, could use sounds emitted by a plant to gain information about the plant’s condition. More investigation on plant bioacoustics in general and on sound emission in plants in particular may open new avenues for understanding plants and their interactions with the environment, and it may also have a significant impact on agriculture.

[www.livescience.com]
Plants 'Scream' in the Face of Stress

By Nicoletta Lanese - Staff Writer 5 days ago

A new study suggests that plants that are stressed by drought or physical damage may emit ultrasonic squeals.

In times of intense stress, people sometimes let out their angst with a squeal ?— and a new study suggests that plants might do the same.

Unlike human screams, however, plant sounds are too high-frequency for us to hear them, according to the research, which was posted Dec. 2 on the bioRxiv database. But when researchers from Tel Aviv University in Israel placed microphones near stressed tomato and tobacco plants, the instruments picked up the crops' ultrasonic squeals from about 4 inches (10 centimeters) away. The noises fell within a range of 20 to 100 kilohertz, a volume that could feasibly "be detected by some organisms from up to several meters away," the authors noted. (The paper has not been peer reviewed yet.)
...
In previous studies, researchers affixed recording devices directly to plants to listen for secret sounds inside their stems. In plants stressed by drought, air bubbles formed, popped and triggered vibrations within the tissue that normally carries water up the plants' stems. The process, known as cavitation, was picked up by the attached recording devices, but the Tel Aviv researchers wanted to know if any plants sounds could travel through the air.

So the team set up microphones near stressed-out tomato and tobacco plants placed in either a soundproof box or an open greenhouse space. The researchers subjected one set of crops to drought conditions and another to physical damage (a snipped stem). A third untouched group served as a point of comparison.

The recordings revealed that the different plant species made distinct sounds at varying rates, depending on their stressor. Drought-stressed tomato plants emitted about 35 ultrasonic squeals per hour, on average, while those with cut stems made about 25. Drought-stressed tobacco plants let out about 11 screams per hour, and cut crops made about 15 sounds in the same time. In comparison, the average number of sounds emitted by untouched plants fell below one per hour.



Edited 1 time(s). Last edit at 12/12/2019 04:19AM by Tai.

While there is some skepticism about just "who" plants are and what they are capable of knowing and feeling, even the skeptics "don't dispute that plants are extremely aware of their environment, and are able to process and integrate information in sophisticated ways. In fact, a plant's awareness of its environment is often keener than an animal's precisely because plants cannot flee from danger and so must sense and adapt to it." In another essay in New Scientist called "Rooted in experience: The sensory world of plants," you can read about research that shows that plants see light and have a sense of smell, taste, touch, and hearing.