The world is filled with sounds and they play a role in living and surviving. Thinking about this caused Tel Aviv University researcher Lilach Hadany to wonder whether it wasn’t just animals that could sense sound, but plants too.
The first experiments to test this hypothesis, published on the pre-print server bioRxiv, suggest that in at least one case, plants can hear, and it results in a real evolutionary advantage.
Hadany’s team looked at evening primroses (Oenothera drummondii) and found that within minutes of sensing vibrations from pollinators’ wings, the plants temporarily increased the concentration of sugar in their flowers’ nectar. The flowers effectively themselves served as ears, picking up the specific frequencies of bees’ wings while tuning out irrelevant sounds like wind.
Hadany told National Geographic that as an evolutionary theoretician, her question was prompted by the realization that sounds are a ubiquitous natural resource – one that plants would be wasting if they didn’t take advantage of it as animals do.
Her team started by investigating flowers, as pollination is key to plant reproduction. They chose evening primrose, which grows wild around Tel Aviv, as it has a long bloom time and produces measurable quantities of nectar.
Hadany’s team exposed plants to five sound treatments – silence, recordings of a honeybee from ten centimetres away, and computer-generated sounds in low, intermediate, and high frequencies. Plants that were not exposed to sound and that were placed under vibration-blocking glass jars had no significant increase in nectar sugar concentration. The same went for plants exposed to high-frequency and intermediate-frequency sounds.
However plants exposed to playbacks of bee sounds and similarly low-frequency sounds, responded within three minutes with increased sugar concentrations.
The team concluded that sweeter nectar for pollinators, may attract more insects, potentially increasing the chances of successful cross-pollination.
Flowers function as ears
The scientists went into the experiments with a hypothesis that plants can pick up the vibrations of sound waves, and that this might be part of the reason many plants’ flowers are bowl shaped, which makes them perfect for receiving and amplifying sound waves, much like a satellite dish.
To test the vibrational effects of each sound frequency test group, Hadany and her team put the evening primrose flowers under a laser vibrometer which measures tiny movements. The team then compared the flowers’ vibrations with those from each of the sound treatments.
Hadany said it was exciting to see the vibrations of the flower match up with the wavelengths of the bee recording.
This single study has opened up an entirely new field of scientific research, which Hadany calls phytoacoustics.
Marine Veits, Hadany’s co-author said she hopes the work will affirm the idea that it doesn’t always take a traditional sense organ to perceive the world.
“Some people may think, wow can plants hear or smell? I’d like people to understand that hearing is not only for ears.”
Source: Capricorn Review