A recent study conducted by the Massachusetts Institute of Technology (MIT) in the United States has found that plants have the ability to perceive sound, particularly being able to hear the sounds produced by rainfall. The experiment demonstrated that rice seeds exposed to rain sounds germinate faster than seeds that were not exposed to such sounds.
The research team immersed rice seeds in shallow water for observation and discovered that the sound waves generated by raindrops can effectively awaken dormant seeds, leading to early sprouting compared to seeds not subjected to the same sound vibrations.
This experiment marks the first direct evidence in the scientific community that plant seeds and seedlings can perceive sounds in nature. The research team published their findings in the journal “Scientific Reports” in April of this year.
Rice was chosen as the ideal subject for the study due to its ability to germinate in both soil and shallow water environments. The researchers speculate that many other plant seeds with similar characteristics may also possess the ability to perceive rain sounds.
The team proposed a hypothesis to explain how seeds achieve this: when rainwater falls on the surface of a water puddle or the ground, it generates sound waves that cause vibrations in the surrounding environment, including the seeds in shallow water. These vibrations may be strong enough to displace the “statoliths” within the seeds.
“Statoliths” are tiny gravity-sensing organelles within seed cells that have higher density than the cell cytoplasm, allowing them to move and settle within the cell, serving as one of the sources for plants to sense gravity. When the statolith settles at the bottom of the cell, its position reflects the direction of gravity, serving as a signal to guide the growth of roots or shoots in the seeds.
The research team utilized mathematical calculations to determine whether the physical vibrations produced by raindrops could disrupt the statoliths within the seeds. If proven true, this hypothesis will support the mechanism through which sound can directly stimulate plant growth.
In their calculations, the researchers included factors such as the size of raindrops and their terminal velocity (the constant speed reached by a falling object) to estimate the amplitude of the acoustic vibrations produced by the raindrops. The results aligned with the experimental findings on rice seeds: indeed, rain sounds can cause displacement and movement of the statoliths within the seeds, potentially being the fundamental reason for plants to “sense” rain sounds and grow rapidly.
Nicholas Makris, a mechanical engineering professor at MIT and one of the study’s authors, stated, “There have been many excellent studies worldwide revealing the mechanisms through which plants perceive gravity. Our research suggests that this mechanism appears to enable seeds to perceive rain sounds and determine whether their depth in soil or water is conducive to survival.”
In the experiment, the research team submerged approximately 8000 rice seeds in shallow water containers, subjecting some seeds to drip tests to simulate different intensities of rainfall, such as light rain, moderate rain, and heavy rain. These seeds were not directly touched by water droplets but only influenced by the sound waves.
Furthermore, they used underwater hydrophones to measure the acoustic vibrations produced by raindrops in water, comparing the data with recordings of rainy days in natural environments like water puddles, ponds, wetlands, and soil. The results confirmed that the raindrops in the lab could indeed generate acoustic vibrations similar to those in natural rainfall.
The researchers found that the germination speed of seeds exposed to simulated rain sounds increased by 30% to 40% compared to the control group not exposed to rain sounds. Seeds closer to the water surface or soil surface could perceive the sound of water droplets more efficiently and accelerate growth.
The experimental results indicate that seeds capable of perceiving rain sounds may possess biological advantages: when seeds can respond to rain sounds, it often signifies that they are located in shallower soil layers, which facilitate water absorption and smooth sprouting.
Makris emphasized, “The study shows that seeds can perceive sound in some way, and this ability is beneficial for their survival. Additionally, the energy brought by rain sounds may also accelerate the growth of seeds.”