I don’t grow indoor plants. I have a garden full of new ones I’ve planted outside, but I simply cannot keep indoor ones alive.
And it appears that they might have been screaming at me as I accidentally killed them but I just couldn’t hear.
There is a growing body of work that provides evidence for plants being able to sense sounds around them. Now, new research suggests they can also generate airborne sounds in response to stress (such as from drought, or being cut). A team at Tel Aviv University has shown tomato and tobacco plants not only make sounds, but do so loudly enough for other creatures to hear.
Instead, they’ve evolved complex biochemical responses and the ability to dynamically alter their growth (and regrow body parts) in response to environmental signals including light, gravity, temperature, touch, and volatile chemicals produced by surrounding organisms.
These signals help them maximise their growth and reproductive success, prepare for and resist stress, and form mutually beneficial relationships with other organisms such as fungi and bacteria.
How do they know?
To carry out their research, the team placed microphones 10cm from plant stems that were either exposed to drought (less than 5 per cent soil moisture) or had been severed near the soil. They then compared the recorded sounds to those of unstressed plants, as well as empty pots, and found stressed plants emitted significantly more sounds than unstressed plants.
And there’s audio! This has been adapted so humans can hear it as pops.
The number of pops increased as drought stress increased (before starting to decline as the plant dried up). Moreover, the sounds could be detected from a distance of 3-5 metres – suggesting potential for long-range communication.
What to make of this?
It’s tempting to speculate these airborne sounds could help plants communicate their stress more widely. Could this form of communication help plants, and perhaps wider ecosystems, adapt better to change?
Or perhaps the sounds are used by other organisms to detect a plant’s health status. Moths, for example, hear within the ultrasonic range and lay their eggs on leaves, as the researchers point out.
Then there’s the question of whether such findings could help with future food production. The global demand for food will only rise. Tailoring water use to target individual plants or sections of field making the most ‘noise’ could help us more sustainably intensify production and minimise waste.