Plants Make Sounds In Dangerous State

 Oleg Loginov

It seems that Roald Dahl has finally guessed something: when plants are harmed, they emit sound signals - not exactly the way people or animals do, emitting screams, but in the form of beeping or clicking sounds at ultrasonic frequencies beyond the limits of human hearing. These sound signals increase in intensity as the plant becomes stressed. According to a recent study, this phenomenon may be a means by which plants communicate their plight to the outside world.

Lilah Hadani, an evolutionary biologist at Tel Aviv University in Israel, noted: “Even in a quiet field, there are sounds that we cannot hear, and these sounds convey information. Some animals are able to detect these sounds, which suggests the possibility of widespread acoustic interaction.” Plants constantly interact with insects and other creatures, many of which use sound to communicate. Therefore, it would be suboptimal if plants did not use sound as a means of communication.

Plants under stress are more dynamic than one might expect. They undergo significant changes, including releasing strong aromas and changing colour and shape. These changes serve as a danger signal to neighbouring plants, prompting them to strengthen their defences or attract animals that can cope with pests that are harming the affected plant.

However, the question of the extent to which plants emit various signals, such as sounds, has not yet been studied. A few years ago, Hadani and her colleagues demonstrated that plants can perceive sound. This led them to wonder whether plants could also make sound.

To investigate this issue, they recorded the sounds of tomato and tobacco plants under various conditions: no load, dehydrated, and stemmed. The recordings were made both in a soundproof acoustic chamber and in standard greenhouse conditions. Then a neural network algorithm was trained to distinguish between the sounds made by plants in different states.

The sounds produced by the plants resemble pops or clicks at frequencies too high for human perception, detectable over a radius of more than a meter. Plants that are not stressed are usually silent. In contrast, stressed plants make more noise, averaging about 40 clicks per hour depending on the plant species. Dehydrated plants have a characteristic sound profile: they begin to click more frequently before visible signs of dehydration appear, become louder as the plant becomes more dry, and decrease as the plant wilts.

The algorithm successfully distinguished these sounds and even identified the types of plants producing them. Moreover, it was not limited to just tomatoes and tobacco: other plants also made sounds, including wheat, corn, grapes, cactus and shrubs.

For humans, the implications of this are clear: we can monitor the sounds made by thirsty plants and give them water before they become severely dehydrated. However, the question of whether other plants are able to perceive and respond to these sounds remains unexplored. Previous research has shown that plants can increase their drought tolerance in response to sound, making this a plausible topic for further study.

-- Pravda.ru