Advances in Investigating Plant Communication Through Sound

Plants are capable of emitting ultrasonic sounds when they are stressed, according to a recent study. These high-frequency noises, which are outside the range of human hearing, serve as a form of communication by informing other organisms about the plant’s distress. Evolutionary biologist Lilach Hadany from Tel Aviv University explains that even in a quiet field, there are sounds that humans cannot perceive but carry information. Since many animals use sound for communication, it is logical to assume that plants would also utilize sound in their interactions with insects and other animals.

Plants’ Ultrasonic Communication

Contrary to popular belief, plants under stress do not remain passive. They undergo noticeable changes such as emitting strong odors, altering their color and shape, and even producing sound. These changes can serve as warning signals to nearby plants, prompting them to enhance their own defenses or attract animals to deal with pests that may be damaging the plant. While previous studies have confirmed that plants can detect sound, researchers were interested in determining if plants could also produce sound.

Evidence of Plant Sound Production

In order to investigate this, the team recorded tomato and tobacco plants under various conditions. They recorded both unstressed plants, as well as plants that were dehydrated or had their stems cut. The recordings were conducted in both a soundproofed acoustic chamber and a regular greenhouse environment. A machine learning algorithm was then trained to differentiate between the sounds emitted by the different types of plants.

Stress-Induced Changes in Plants

The sounds plants make are similar to popping or clicking noises, but at frequencies that humans cannot perceive. These sounds can be detected within a radius of over a meter and are more prevalent in stressed plants, with the number of clicks increasing depending on the plant species. For example, stressed plants can produce an average of up to 40 clicks per hour. Dehydrated plants exhibit a distinct sound profile, with clicking noises escalating as the plant’s water levels decrease and subsiding as the plant withers. The team also discovered that various plant species, including wheat, corn, grape, cactus, and henbit, are capable of sound production.

However, there are still unanswered questions regarding this phenomenon. It remains unclear how plants produce these sounds, although previous research has indicated that cavitation – the formation, expansion, and collapse of air bubbles in the stem – may contribute to the popping noises. Additionally, it is unknown if other stressors like pathogens, attacks, UV exposure, or extreme temperatures can induce sound in plants. The team demonstrated that an algorithm can successfully identify and distinguish between different plant sounds, suggesting that other organisms could also potentially interpret these sounds and respond to them.

Understanding the Significance of Plant Sounds: The implications for humans are significant. By tuning into the distress calls of thirsty plants, we have the ability to provide them with water before it becomes a problem. Furthermore, it is plausible that other plants are also capable of sensing and responding to these sounds, as previous research has shown that plants can increase their drought tolerance in response to sound. The next stage of research for the team involves investigating the responses of other organisms, both animals and plants, to these plant sounds, as well as exploring the interpretation of these sounds in natural environments.