Scientists at Bristol University used powerful loudspeakers to listen to corn saplings, and heard clicking sounds coming from their roots. It is yet more evidence that while they appear to be passively swaying in the breeze, plants are in fact actively communicating with each other in a constant chatter.
When they suspended their roots in water and played a continuous noise at a similar frequency to the clicks, they found the plants grew towards it.
Plants are known to grow towards light, and research earlier this year from Exeter University found cabbage plants emitted a volatile gas to warn others of danger such as caterpillars or garden shears. But the researchers say this is the first solid evidence they have their own language of noises, inaudible to human ears, the Daily Mail reported.
Their study is published in the journal Trends in Plant Science. They suspect sound and vibration may play an important role in the life of plants. Daniel Robert, a biology professor at Bristol, said: "These very noisy little clicks have the potential to constitute a channel of communication between the roots".
Lead author Monica Gagliano, from the University of Western Australia, said it makes sense for plants to produce and respond to sound vibrations, as it gives them information about the environment around them. Sound waves can travel easily through soil and she suggested it could be a way of picking up threats such as drought from their neighbours further away.
"Everyone knows that plants react to light, and scientists also know that plants use volatile chemicals to communicate with each other, for instance, when in danger, such as a herbivore, approaches," she said.
Gagliano said the research "opens up a new debate on the perception and action of people towards plants" which are not objects but should perhaps be treated as "living beings in their own right". Her research also involved placing sweet fennel, known to release chemicals that hamper the growth of other plants, near chili seeds.
When the chemicals were allowed to reach the chili seed, their growth was hampered as expected. But when the chemicals were prevented from reaching them, they grew faster than expected.
The scientists believe the faster-growing seeds were still able to sense the presence of the fennel, probably by detecting a noise or vibration and grew faster to protect themselves.