Gardeners beware – your plants know what you’re doing to them
The next time you prune and harvest or forget to water, think about this!
We’re used to stories about people talking to their plants, even playing music to them. But now it seems the plants have been chatting back. It’s just that we haven’t been listening.
For the first time, scientists from Tel Aviv University have recorded and analysed sounds distinctly emitted by plants.
They make click-like noises, like the popping of popcorn but at high frequencies beyond the range of the human ear.
The researchers found plants usually emit sounds when they are under stress, and that each plant and each type of stress is associated with a specific identifiable sound.
The sounds are probably heard by various animals, such as bats, mice, and insects, as part of the plant’s survival mechanism.
In 2019, researchers showed the buzzing of bees can cause plants to produce sweeter nectar. Others have shown that white noise played to Arabidopsis, a flowering plant in the mustard family, can trigger a drought response.
Using machine learning algorithms, the researchers distinguished not only which species produced the sound, but also what type of stress it was suffering from.
The plants were placed in an acoustic box in a quiet, isolated basement with no background noise. Ultrasonic microphones recording sounds at frequencies of 20-250 kilohertz (the maximum frequency detected by a human adult is about 16 kilohertz) were set up at a distance of about 10cm from each plant.
The study focused mainly on tomato and tobacco plants, but wheat, corn, cactus, and a mint-like weed called henbit were also recorded.
Some of the plants had not been watered for days, some had their stems cut and some were untouched.
The unstressed plants emitted less than one sound per hour, on average, while the stressed plants – both dehydrated and injured – emitted dozens of sounds every hour.
The researchers concluded the world around us is full of plant sounds, and these sounds contain information – for example about water scarcity or injury.
They also believe plant sounds are detected by animals including bats, rodents, and insects – and possible by other plants.
The sounds are used by other creatures to detect a plant’s health status. Moths, for example, hear within the ultrasonic range and lay their eggs on leaves.
The discovery opens up the potential for humans to better understand plants and respond to their needs. For example, with the right sensor gardeners could more accurately know when their plants are stressed and need watering.
This could have commercial benefits for farmers as well as home gardeners in the production of food.
At a time when the demand for food will only rise, tailoring water use to target individual plants or sections of field making the most “noise” could help with sustainable intensified production and minimise waste.
Meanwhile, home gardeners who’ve set up sensors in their veggie patches may be able to receive stress notifications from their neglected plants on their mobile phones.
Related stories: Science Alert, University of Queensland, Tel Aviv University
