Scientific Study: Plants May Hear the Sound of Rain Approaching

SadaNews - A new study conducted by researchers at the Massachusetts Institute of Technology (MIT) revealed that rice seeds are capable of hearing the sound of rain.

The institute described these findings as "the first direct evidence of the ability of plant seeds and seedlings to sense sounds in nature." Interestingly, the effects observed in the study are not as radical as they may seem.

This was reported in a piece prepared by Stuart Thompson, a senior lecturer in plant biochemical technology at the University of Westminster, and published on Refractor.

Music

Playing music for plants might seem strange, but some previous studies have found that it actually has an effect. For example, a study in 2024 showed that bok choy plants grow better with classical music, while their growth is of lower quality with rock and roll music. This is not an isolated case, as sound can influence plant behavior in various ways.

For instance, some flowers use the buzzing frequency of insects to determine whether to release pollen. Both Arabidopsis and tobacco plants produce higher levels of toxins, such as nicotine, in response to the sound of larvae chewing on nearby plants. There are also reports indicating that tones emitted from a synthesizer can enhance seed germination and seedling growth in green beans, cucumbers, and rice.

The Sound of Rain

Unlike previous experiments that used electronic tones from speakers, MIT researchers this time tested the effect of a natural sound on rice germination, specifically the sound of rain, as rice can grow in soil or underwater.

The researchers began by measuring the sound produced by raindrops falling on shallow ponds that resembled the rice fields where they planted the seeds. The sound level generated by the droplets hitting the water was extremely high, equivalent to a person shouting directly in your ear, but was mostly at very low or very high frequencies that humans cannot hear.

They then simulated rain falling on some ponds containing rice and compared the germination rates with seeds in still water. They found that while the droplets simulating light rain had a limited effect, heavier rain contributed to increased germination, with heavier rainfall boosting the germination rate by more than 30%.

They also reached important evidence from a previous study about how rice can sense sound. A study conducted in 2002 found that mutant Arabidopsis plants, which cannot produce starch, did not respond to vibrations in the same way as normal plants did.

Sound Waves

Sound waves are simply vibrational energy traveling through gas, liquid, or solid bodies, causing the objects they pass through to vibrate, such as the eardrum membranes we use for hearing.

While sound is one way to sense vibrations, MIT researchers hypothesized that plants might need the ability to produce starch to be able to sense sound.

This drew their attention to structures called "statoliths", which are high-density particles.

Plant cells capable of sensing gravity contain several statoliths filled with extremely dense starch, causing them to sink within the cell. When they sink, these statoliths rub against other structures inside the cell, then settle at the bottom, telling the plant which way is down.

The Effect of Sound on Statoliths

To test their hypothesis, researchers simulated the effect of recorded sound on the statoliths inside rice seeds, finding that the sounds of rain could make these statoliths jump from the bottom of the cell like grains on the surface of a drum.

The effect of light rain is limited, but as the intensity of the sound increases, the statoliths jump higher and faster, corresponding with the stimulation of the germination process.

The layer of statoliths at the bottom of the cell appeared to behave like a quasi-liquid, similar to balls in a children’s play pool, and the energy from sound moves this "liquid" and helps spread chemical messages to other parts of the plant.

The mutant Arabidopsis plants in the previous study likely could not sense vibrations because they cannot produce the starch needed to make statoliths, which suggests that statoliths might be one of the ways in which plants "hear".

While scientists no longer doubt plants' ability to detect and respond to sounds, the question remains: Is this actual hearing, or does signal perception require a mind?

Plants do not possess a nervous system or central brain like humans and most other animals. Nonetheless, there is extensive debate among scientists about whether plants exhibit a form of intelligence or not.

Electrical Signals

Observations of plant behaviors that appear intelligent include a study conducted in 2017, where pea plant roots seemed to follow the sound of water through a simple maze, as well as research from 2016 indicating that pea shoots learned they could find light if they followed the direction of wind produced by a fan.

Scientists have observed electrical signals in plants that are somewhat similar to those in our nerves, even if they are not transmitted through specialized structures like our nervous system. In many cases, we do not know their function, possibly because plants often respond in ways that are not obvious to us.

For instance, electrical signals are used to trigger the "Venus flytrap" to close its trap and crush its prey. They are also employed in the Mimosa pudica (known as the sensitive plant), which closes its leaves rapidly when touched. There may be a more dispersed or decentralized form of intelligence possible in plants.

There may also be other influencing factors. Hearing might require a living being that is conscious of sounds. While there are many definitions of consciousness, the two scientists Lynn Margulis and Dorian Sagan (mother and daughter) have argued that consciousness in its simplest form is merely awareness of the external world. If that is the case, all organisms must possess this level of awareness to respond to their environment and survive, even if the degree and complexity of that awareness varies.

In conclusion, the world of the small rice plant might be entirely different from ours in ways that make it difficult to understand, but it may not be an exaggeration to say that it "hears" the sound of rain.