Tikalon Blog by Dev Gualtieri

Plant Sounds

August 5, 2024

My early adulthood coincided with the New Age movement and its belief in many discredited past ideas, one of which was astrology. We are supposedly living in the start of a 2,160 year Age of Aquarius, one of the twelve zodiacal divisions of the 5,920 year period of Earth's precession, called a Great Year. The anthem of this age is the song, The Age of Aquarius made popular by the American musical group, The 5th Dimension.[1] This was the most popular song for a six week period in 1969, and it's listed as one of Billboard's Greatest Songs of All Time in 2024, 55 years after its release.[2] This list is changeable; so, the song might be off the list sometime in the future.

Gaia entrusts Erichthonius. the child of Hephaestus and Gaia the Earth goddess. to Athena (Marble relief)

In this marble relief at the Louvre museum, Gaia, the Greek goddess who was the mother of all life, entrusts Erichthonius, her child with Hephaestus, to Athena. This relief is thought to have come from the temple of Hephaestus in Athens.

James Lovelock (1919-2022) named his Gaia hypothesis after Gaia.

(Portion of a Wikimedia Commons image, enhanced to show detail, by Gary Todd. Click for larger image.)

Coincident with the New Age movement was the formulation of the Gaia hypothesis by British scientist, James Lovelock (1919-2022). This hypothesis was that the Earth's biophysical environment was synergistic and self-regulating, acting like a single organism with the goal of self preservation. Scientists have always been critical of the Gaia hypothesis, since it's a teleological argument similar to many such arguments proposed by Aristotle. However, the Geological Society of London awarded Lovelock its Wollaston Medal in 2006.

One New Age idea that seemed strange at the time was that talking to plants helped them to grow. What could be more New Age than a hippie chick talking to a potted plant? However, a scientific study by the Royal Horticultural Society (RHS) has shown that this actually works, and it works better when women speak than men.[3-4]

Leigh French as Goldie Keif, the Hippie Chick, from The Smothers Brothers Comedy Hour.

French's segment of the show was called "Share a Little Tea with Goldie."

(Screenshot from a YouTube video by The Smothers Brothers, October 21, 2023. Click for larger image.)

Apparently, the idea that plants respond to speech was first mentioned in the 1848 book, Nanna, by German psychologist, Gustav Fechner (1801-1887).[4] In the RHS experiment, recordings were made of male and female speakers reading excerpts from The Day of the Triffids by John Wyndham, Shakespeare's's A Midsummer's Night Dream, and Charles Darwin's On the Origin of Species. These recordings were played to ten tomato plants for more than a month, and there were two control plants grown in silence.[3-4]

The experiment showed that plants grew an inch higher when exposed to women's voices than for men's voices.[3-4] One of the woman readers was Sarah Darwin, the great-great granddaughter of Charles Darwin, who read a portion of his On the Origin of Species.[3-4] Her plant grew almost two inches taller than that of the best performing male.[3-4] Charles Darwin himself did an experiment in which he played a bassoon to a mimosa plant, thinking it might close its leaves as it does when gently touched.[5] There was no response; but a bassoon is a low register musical instrument that would resemble a male voice more than a female voice. Plants exposed to wind produce ethylene, a growth retarding chemical that results in shorter plants with thicker stems, and this mechanism might somehow be involved.[4]

Not only do plants respond to speech, but they also emit sound when they're in distress. An open access article appearing last year in the journal, Cell, by scientists from Tel Aviv University (Tel-Aviv, Israel) relate their experimental finding that tomato plants and tobacco plants will emit loud ultrasonic popping sounds when stressed from dehydration, or by having their stems cut.[6-9] Although these sounds are too high in frequency to be heard by humans, they are likely to be heard by insects, some other mammals; and, possibly, other plants.[7] The amplitude of the sound is at a level similar to that of human speech.[8]

In the experiments, microphones recorded sounds from healthy and stressed tomato and tobacco plants, both in a soundproofed acoustic chamber, and then in a greenhouse.[7] the plants were stressed in two ways, by withholding water for several days, and by cutting the plant stems.[7] Tomato and tobacco plants were selected for study, since they are easy to grow, but it was found that corn, wheat, grape, and cactus plants also emit sounds when they are stressed.[7] The resultant plant sounds resemble pops or clicks (listen to example), with each stressed plant emitting about 30-50 clicks per hour at random intervals.[7] Unstressed tomato plants were very quiet.[7] After peaking at five days, water stressed plants emitted sound at a decreased rate until they were completely dried.[7]

Montage of tomato plant popping sounds shifted to audible frequencies , with some background music, as extracted from a YouTube video.[8] The recorded plant sounds are released under a Creative Commons 1.0 Universal Public Domain Dedication license at ref. 9.[9]

Members of the research team had previously found that plants increase their sugar content when they hear sounds made by pollinators.[7] Although the mechanism of the sound generation in plants is not known, the research team conjectures that it might arise from the formation and bursting of air bubble in the plant's vascular system.[7] They also conjecture that other organisms could have evolved to hear and respond to these sounds.[7] One possible application of this research is monitoring plants to determine when irrigation is needed, thereby conserving water.[7]

Audio spectrum of plant sounds. (Figure 1d of ref. 6, released under a Creative Commons License.[6] Click for larger image.)

Plant Sounds

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