In the great symphony of nature, where every organism seems to have its own unique way of expressing its needs and emotions, the plant kingdom has long been considered silent. However, recent research has revealed a surprising revelation: garden plants, like suffering humans, emit sounds when they find themselves in adverse conditions. This botanical symphony, though inaudible to the human ear without the aid of microphones, may hold clues to the mysterious language of flora.
The study, carried out by a team of researchers, analyzed the acoustic emissions of tomato and tobacco plants. To capture these subtle sounds, the scientists placed the plants in a soundproof acoustic chamber. The study included both healthy and stressed plants, the latter subjected to the torment of lack of water or stem cutting. The recordings revealed a surprising chorus of high-pitched noises, similar to pops or clicks. Stressed plants were found to produce between 25 and 35 of these sounds per hour, while their calm counterparts only emitted one sound per hour.
The researchers took the experiment a step further by developing a machine learning algorithm capable of distinguishing between stressed and non-stressed plants. Testing the algorithm in a bustling greenhouse, the team successfully filtered out background noise, revealing that the cries of distressed plants could still be discerned. Impressively, the algorithm demonstrated 70% accuracy in identifying whether a plant was stressed due to dehydration or stem cutting.
Plants in the garden emit sounds imperceptible to the human ear
The question arises: how do plants, lacking vocal cords or lungs, produce these enigmatic sounds? The researchers propose a mechanism known as cavitation in xylem, the tubes responsible for transporting water inside the plant. Under stressful conditions, air bubbles can form in the xylem, and the hypothesis suggests that the sounds observed in the study result from the formation or bursting of these bubbles.
With this new knowledge in hand, researchers ponder the next intriguing question: Who might be the intended audience for these botanical ballads? Surprisingly, they are not human because the sounds are too loud for our ears to detect without help. Instead, the researchers suggest that other members of the natural world—mammals, insects, and even other plants—may be adapted to these ultrasound emissions.
Lead author Lilach Hadany suggests that the ability to make sounds could be an evolutionary adaptation for plants. Because plants constantly interact with insects and other animals, many of which use sound to communicate, making sounds could be a strategic move. Hadany speculates that organisms such as moths planning to lay eggs on a plant or animals contemplating a leafy feast could use these sounds as cues for decision-making, according to iflscience.com.