Plants’ Screams Detected for the First Time

Roald Dahl’s concept may have validity: plants emit sounds when subjected to harm. However, these sounds differ from human screams. They manifest as popping or clicking noises in ultrasonic frequencies beyond the human auditory range, intensifying when the plant undergoes stress.

According to a study published in 2023, this could represent one of the methods through which plants convey their distress to their surroundings.

“Even in seemingly tranquil environments, there exist sounds beyond our perception that carry information. Certain animals possess the ability to perceive these sounds, suggesting the potential for significant acoustic interactions,” stated Lilach Hadany, an evolutionary biologist at Tel Aviv University in Israel.

“Given that plants regularly interact with insects and other creatures, many of which utilize sound for communication, it would be inefficient for plants to disregard sound altogether.”

Plant Responses to Stress

Contrary to common perception, plants undergoing stress exhibit notable changes. Among the most noticeable alterations, recognizable to humans, are the release of potent aromas and modifications in color and shape.

These alterations serve as signals of danger to neighboring plants, prompting them to enhance their defensive mechanisms or attract animals to address potential pests threatening the plant.

Despite these observations, the extent to which plants emit various signals, including sounds, remains largely unexplored. Hadany and her colleagues previously discovered that plants can perceive sound, prompting the inquiry into whether they can also produce it.

To investigate, researchers recorded tomato and tobacco plants under various conditions.

Initially, they recorded unstressed plants to establish a baseline. Subsequently, they recorded plants subjected to dehydration and those with their stems cut. These recordings were conducted both in a soundproofed acoustic chamber and in a typical greenhouse setting.

Next, they employed a machine learning algorithm to discern the differences in sound emitted by unstressed plants, cut plants, and dehydrated plants.

The sounds emitted by plants resemble popping or clicking noises, occurring at frequencies too high for human perception, detectable within a range exceeding one meter (3.3 feet). Unstressed plants emit minimal noise, simply going about their usual activities in a quiet manner.

Amplified Noise Levels in Stressed Plants

In contrast, stressed plants exhibit considerably more noise, with an average emission of up to approximately 40 clicks per hour depending on the plant species.

Plants deprived of water demonstrate a distinct sound profile, with increased clicking occurring before visible signs of dehydration, intensifying as the plant becomes increasingly parched, and gradually diminishing as the plant wilts.

The machine learning algorithm successfully differentiated between these sounds and even identified the plant species emitting them. Notably, this phenomenon is not limited to tomato and tobacco plants.

The research team tested various plant species and found that sound production appears to be a widespread activity among plants. Wheat, corn, grape, cactus, and henbit were among those recorded emitting noise.

However, there are still several uncertainties. For instance, the mechanism behind sound production remains unclear.

Previous studies suggest that dehydrated plants undergo cavitation, a process where air bubbles in the stem form, expand, and collapse—similar to the phenomenon observed in human knuckle cracking, resulting in an audible pop. It’s yet to be determined if other stressors, such as pathogens, attacks, UV exposure, or extreme temperatures, can induce similar sound emissions in plants.

Unanswered Questions on Plant Sound Production

Furthermore, it’s uncertain whether sound production in plants is an adaptive trait or simply an incidental occurrence. However, the study showcased the feasibility of training an algorithm to discern and distinguish among various plant sounds, suggesting the potential for other organisms to possess comparable abilities.

Moreover, these organisms may have evolved to react to the distress signals emitted by plants in various ways.

“For instance, a moth looking to lay eggs on a plant or an animal seeking to consume a plant could utilize these sounds to inform their decisions,” noted Hadany.

For humans, the implications are straightforward; we could potentially detect the signals of thirsty plants and provide them with water before it becomes problematic.

However, it remains uncertain whether other plants are capable of sensing and responding to these signals. Previous studies have indicated that plants can enhance their tolerance to drought in response to sound, suggesting this possibility. This aspect constitutes the focus of the team’s forthcoming research.

“Now that we have confirmed that plants emit sounds, the next inquiry is, ‘who might be listening?‘” Hadany remarked.

“We are currently examining the reactions of other organisms, including both animals and plants, to these sounds, and we are also exploring our ability to identify and interpret the sounds in natural environments.”

Read the original article on: Science Alert

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