What if plants had a musical ear? Australian researchers have discovered that playing a monotonous sound stimulates the activity of a microscopic soil fungus known to promote plant growth.
Faced with erosion, agricultural overexploitation, deforestation and pollution, restoring soils is a growing challenge to preserve biodiversity and produce crops sustainably.
There are many technologies: improvement of the soil structure to promote water retention, reintroduction of organic matter, reduction in the use of pesticides, inoculation of microbes, etc.
“However, the role of acoustic stimulation in this area remains little explored,” notes a team of researchers from Flinders University (South Australia), in a study published Wednesday in the “Biology Letters” of the British Royal Society.
Based on previous work on the exposure of the E. Coli bacteria to sound waves, these biologists wanted to evaluate the effect of acoustic stimulation on the growth rate and production of spores – or sporulation – of Trichoderma harzianum.
This microscopic fungus is often used in organic agriculture for its abilities to protect plants from pathogens, improve nutrient utilization and promote growth.
– White noise –
To conduct their experiment, they built and installed sterilized sound attenuation chambers, into which they placed petri dishes where the fungus was grown.
They then broadcast in one of these rooms “Tinnitus Flosser Masker at 8kHz”, one of the many white noise videos available on YouTube, supposed to relieve tinnitus or help babies fall asleep.
“It resembles the sound of an old radio between two stations,” Jake Robinson, one of the co-authors of the study, told AFP. “We chose this monotony for controlled experimental reasons, but it is possible that a more diverse or natural soundscape would be more effective. This requires further research,” he says.
The petri dishes were exposed to this soundscape broadcast at a level of 80 decibels for thirty minutes per day.
After five days, the growth and sporulation rates of fungi subjected to acoustic stimulation were higher than those of specimens placed in the chambers without a soundscape.
The researchers put forward several potential mechanisms to explain these results.
They could be due to a piezoelectric effect, by which a mechanical pressure (here an acoustic wave) is converted into an electric charge. These phenomena can influence cellular and molecular processes in living organisms, as has already been observed for peptides, amino acids, proteins or viruses.
Another hypothesis is based on the mechanoreceptors that fungi have on their membranes. These are comparable to those present in thousands in human skin and which play a role in the sense of touch, influencing how we react to pressure or vibration.
“It could be that sound waves stimulate these mechanoreceptors in fungi, then triggering a cascade of biochemical events that turn certain genes on or off – for example, genes responsible for growth,” Robinson said.
“Our preliminary research suggests that fungi respond to sound, but we don’t yet know if this benefits plants. So that’s the next step,” explains the biologist.
“Can we influence soil or plant microbial communities as a whole? Can we speed up the soil restoration process by stimulating the land with natural soundscapes? What impact might this have on soil fauna? There are many important questions to occupy us!”, he concludes.
