Engineering the Maestro of the Vegetation Choir
Written by Angela Zhu, Illustration by Lili Lin
Dogs bark, ducks quack, but what about plants? They are thought of as static beings, quietly growing in their own corner so long as there is a bountiful supply of sun, water and dirt. However, even without ears or a mouth, plants actually do “speak” to each other, just in ways imperceptible to our senses. They communicate by sending signals into the air called volatile organic compounds (VOCs)1, by sending chemicals through their roots connected by fungi networks2 and recently, it has been found that they even communicate with sound!3
Indeed, plants have been shown to produce ultrasonic sounds between 20-100 kHz which are hypothesized to be the byproduct of gas bubbles bursting in the xylem. Since different stressors affect gas bubbles differently – a cut would result in an abrupt change whereas dehydration would result in a gradual one – the difference in frequencies, durations, amplitudes and regularities might not only depend the plant’s size but also on the type of stress the plant is exposed to. Case in point, in March 2023, a group of researchers developed a machine learning model that is able to discern a cut plant from a dehydrated one. The model can even evaluate the level of dehydration of the plant! 3
We have established that plants can emit sound, but all that would be for naught if plants cannot “hear”. Fortunately, plants have indeed been shown to respond to sound stimuli and adjust their growth and other characteristics accordingly. For example, they can hear the movements of a pollinator and sweeten their nectar in response, or warn other plants to increase their defenses against destructive herbivores.4 In a study by Abdullah et al., soprano, classic, nature, rock and koranic acting acoustic patterns were played to Mung beans at 60 dB. As expected, the beans grew differently depending on the music, with soprano affecting the length of the leaves whereas the Quranic recitation affected leaf production.1
So how can this knowledge be useful for us? Plant Acoustic Frequency Technology (PAFT) is designed to increase crop growth and productivity by exposing them to the appropriate sound waves thereby reducing the necessity of fertilizers.1 Alternatively, we could “listen” to the plants to determine their needs, and adjust the water provided accordingly for example.3
The developing technologies will equip us with a new pair of ears, allowing us to listen to what the choir is singing or even incite the plants to dance to our own tune.
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