While we're on the subject of unique communication methods, let's take a look at some mildly unsettling scientific findings.
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 [source: Deutsche Welle]. And it's not just cucumbers that are making their voices heard.
Stressed Tomato Plants
For a 2019 study published in the journal Cell, researchers from Tel Aviv University placed microphones near tomato and tobacco plants that were dehydrated or damaged. They were able to detect ultrasonic sounds emitted by the plants from a distance of about four inches. These sounds ranged from 20 to 100 kilohertz, potentially detectable by certain organisms from several meters away.
However, you won't hear these screams while chilling out in the living room near your favorite basil plant because these sounds occur at ultrasonic frequencies beyond human hearing range. When adjusted to frequencies audible to human ears, these bursts of sound caused by stress resemble the sound of someone tap dancing on a field of bubble wrap.
While these ultrasonic bursts are beyond human hearing, they could potentially be perceived by mammals, insects and other plants in their natural environments, prompting corresponding reactions.
Chewing Sounds Put Plants on High Alert
In a macabre turn of events, there's also evidence that plants can hear themselves being eaten. Researchers at the University of Missouri-Columbia found that plants understand and respond to chewing sounds made by caterpillars munching on them. As soon as the plants hear the noises, they respond with several defense mechanisms [source: Feinberg].
For some researchers, evidence of these complex communication systems — emitting noises via gas when in distress — signals that plants can feel some type of pain. Others argue that there cannot be pain without a brain and nervous system to register the feeling. But before you rethink your veggie medley, know that you're not engaging in any botanical torture because these plants are likely not experiencing pain like land animals, sea creatures or other animals.
Still, more scientists surmise that plants can exhibit intelligent behavior without possessing a brain or conscious awareness [source: Pollan].