Ruminations: Plant Communication

"An idyllic field of flowers can be a noisy place. It's just that we can't hear the sounds."
"Our findings suggest the world around us is full of plant sounds, and that these sounds contain information -- for example, about water scarcity or injury."
"We assume that in nature the sounds emitted by plants are detected by creatures nearby, such as bats, rodents, various insects, and possibly also other plants -- that can hear the high frequencies and derive relevant information."
Lilach Hadany, School of Plant Sciences and Food Security, Wise Faculty of Life Sciences, Tel Aviv University

Drew Beaudoin sits on a chair surrounded by dozens of plants.

House plant enthusiast Drew Beaudoin is surprised to learn plants emit sounds. (Katerina Georgieva/CBC)

Scientists in Israel discovered that plants voice their discomfort and distress due to drought, neglect or disease. The human ear cannot detect these sounds that are high-pitched emergency signals of distress. But they recorded the sounds of tomato, tobacco, wheat, corn and cactus making occasional ultrasonic popping noises which the researchers likened to bubble wrap. Plants ramp these sounds up when they're suffering stress. The findings were published in the journal Cell.

Famously, other, previous studies showed that plants respond positively and tend to thrive when exposed to music and to being gently spoken to. Now, science brings us the news that plants also communicate in their very particular biological way that nature has endowed them with; plant speech. Water scarcity or injury provoke plants to distress they aurally broadcast.

The research team placed plants in an acoustic box that was placed in an isolated basement with no background sound. Microphones capable of recording sounds at frequencies of 20 to 250 kilohertz were placed four inches from each plant.The plants were then subjected to different treatments; some left unwatered for five days; others had their stems cut, and a control group was left intact.

Subsequent recordings showed sounds were emitted by the plants at frequencies of 40-80 kilohertz. Unstressed plants produced barely one click every hour on average; the stressed plants emitted dozens of sounds every hour. The maximum frequency detected by a human adult is roughly15 kilohertz.

Noises were emitted by water-sressed plants before they were visibly dehydrated. The researchers found it was possible to identify the distressed plant along with the type of stress being experienced. A dehydrated tomato plant made a different pattern of clicks as compared to a dehydrated cactus. Happy plants on the other hand, had a tendency to be quiet.

The potential for monitoring plants to determine whether they are struggling, based on their noises is a potential for a new type of agricultural program the research team envisions emerging from this research. Sound recordings could conceivably be used in irrigation monitoring crop hydration to help distribute water more efficiently.