Plant bioacoustics

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Plant bioacoustics refers to the creation of sound waves by plants. Measured sound emissions by plants as well as differential germination rates, growth rates and behavioral modifications in response to sound are well documented. [1] Plants detect neighbors by means other than well-established communicative signals including volatile chemicals, light detection, direct contact and root signaling. [2] [3] [4] Because sound waves travel efficiently through soil and can be produced with minimal energy expenditure, plants may use sound as a means for interpreting their environment and surroundings. Preliminary evidence supports that plants create sound in root tips when cell walls break. [5] Because plant roots respond only to sound waves at frequencies which match waves emitted by the plants themselves, it is likely that plants can receive and transduce sound vibrations into signals to elicit behavioral modifications as a form of below ground communication. [6]

Buzz pollination, or sonication, serves as an example of a behavioral response to specific frequencies of vibrations in plants. Some 20000 plants species, [7] including Dodecatheon and Heliamphora have evolved buzz pollination in which they release pollen from anthers only when vibrated at a certain frequency created exclusively by bee flight muscles. The vibrations cause pollen granules to gain kinetic energy and escape from pores in the anthers. [8]

Similar to buzz pollination, there's a species of evening primrose that has been shown to respond to bee wing beats and sounds of similar frequencies by producing sweeter nectar. Oenothera drummondii (beach evening primrose) is a perennial subshrub native to the Southeastern United States, but has become naturalized on almost every continent. [9] The plant grows among coastal dunes and sandy environments. It has been discovered that O. drummondii flowers produce significantly sweeter nectar within three minutes when exposed to bee wingbeats and artificial sounds containing similar frequencies. [10] A possibility for this behavior is the fact that if the plant can sense when a pollinator is nearby, there is a high probability another pollinator will be in the area momentarily. In order to increase the chance of pollination, nectar with a higher sugar concentration is produced. It has been hypothesized that the flower serves as the “ear” which contains mechanoreceptors on the plasma membranes of the cells to detect mechanical vibration. [10] A possible mechanism behind this is the activation of mechanoreceptors by sound waves, which causes a flux of Ca2+ into the plant cell causing it to depolarize [11] Because of the specific frequencies produced by the pollinators’ wings, perhaps only a distinct amount of Ca2+ enters the cell, which would ultimately determine the plant hormones and expression of genes involved in the downstream effect. Research has shown that there is a calmodulin-like gene that could be a sensor of Ca2+ concentrations in cells, therefore amounts of Ca2+ in a plant cell could have substantial effects over the response of a stimuli. [12] Due to the hormones and genes expressed in the petals of the flower, the transport of sugar into the nectar was increased by about 20%, giving it a higher concentration than compared to the nectar of flowers that were exposed to higher frequencies or no sound at all. [10] An LDV (Laser Doppler vibrometer) was used to determine if the recordings would result in vibration of the petals. Petal velocity was shown in response to a honey bee and moth sound signal as well as low frequency feedbacks, but not high frequency feedbacks. [10] Sugar concentrations of nectar was measured before and after the plants were exposed to sound; significant increase in sugar concentration was only observed when the low frequency (similar to bee wingbeats) and bee sounds were played. [10] To validate that the flower was the organ sensing the vibration of the pollinator, an experiment was run where the flowers were covered with a glass jar, while the rest of the plant was exposed. Sugar concentration of nectar showed no significant difference before and after the low frequency sound was played. [10] If petals act like the ears of the plant, then there must be natural selection on the mechanical parameters of the flower. Its resonance frequency depends on size, shape and density. When comparing the traits of plants based on their pollinators, there is a pattern between the shapes of flowers with “noisy” pollinators. Bees, birds and butterflies – the flowers they pollinate all correspond to having bowl-shaped/tubular flowers. [13]

Plants emit audio acoustic emissions between 10–240 Hz as well as ultrasonic acoustic emissions (UAE) within 20–300 kHz. Evidence for plant mechanosensory abilities are shown when roots are subjected to unidirectional 220 Hz sound and subsequently grow in the direction of the vibration source. [6] Using electrograph vibrational detection, structured sound wave emissions were detected along the elongation zone of root tips of corn plants in the form of loud and frequent clicks. When plants are isolated from contact, chemical, and light signal exchange with neighboring plants they are still able to sense their neighbors and detect relatives through alternative mechanisms, among which sound vibrations could play an important role. Furthermore, ultrasonic acoustic emissions (UAE) have been detected in a range of different plants which result from collapsing water columns under high tension. [14] UAE studies show different frequencies of sound emissions based on whether or not drought conditions are present. Whether or not UAE are used by plants as a communication mechanism is not known. [15]

Although the explicit mechanisms through which sound emissions are created and detected in plants are not known, there are theories which shed light on possible mechanisms. Mechanical vibrations caused by charged cell membranes and walls is a leading hypothesis for acoustic emission generation. Myosins and other mechanochemical enzymes which use chemical energy in the form of ATP to produce mechanical vibrations in cells may also contribute to sound wave generation in plant cells. These mechanisms may lead to overall nanomechanical oscillations of cytoskeletal components, which can generate both low and high frequency vibrations. [6]

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<span class="mw-page-title-main">Cochlea</span> Snail-shaped part of inner ear involved in hearing

The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the organ of Corti, the sensory organ of hearing, which is distributed along the partition separating the fluid chambers in the coiled tapered tube of the cochlea.

<span class="mw-page-title-main">Bumblebee</span> Genus of insect

A bumblebee is any of over 250 species in the genus Bombus, part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related genera are known from fossils. They are found primarily in higher altitudes or latitudes in the Northern Hemisphere, although they are also found in South America, where a few lowland tropical species have been identified. European bumblebees have also been introduced to New Zealand and Tasmania. Female bumblebees can sting repeatedly, but generally ignore humans and other animals.

<i>Oenothera</i> Genus of plants

Oenothera is a genus of about 145 species of herbaceous flowering plants native to the Americas. It is the type genus of the family Onagraceae. Common names include evening primrose, suncups, and sundrops. They are not closely related to the true primroses.

<span class="mw-page-title-main">Bioacoustics</span> Study of sound relating to biology

Bioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion and reception in animals. This involves neurophysiological and anatomical basis of sound production and detection, and relation of acoustic signals to the medium they disperse through. The findings provide clues about the evolution of acoustic mechanisms, and from that, the evolution of animals that employ them.

<span class="mw-page-title-main">Buzz pollination</span>

Buzz pollination or sonication is a technique used by some bees, such as solitary bees, to release pollen which is more or less firmly held by the anthers. The anthers of buzz-pollinated plant species are typically tubular, with an opening at only one end, and the pollen inside is smooth-grained and firmly attached. With self-fertile plants such as tomatoes, wind may be sufficient to shake loose the pollen through pores in the anther and accomplish pollination. Visits by bees may also shake loose some pollen, but more efficient pollination of those plants is accomplished by a few insect species who specialize in sonication or buzz pollination.

<span class="mw-page-title-main">Zoophily</span> Pollination by animals

Zoophily, or zoogamy, is a form of pollination whereby pollen is transferred by animals, usually by invertebrates but in some cases vertebrates, particularly birds and bats, but also by other animals. Zoophilous species frequently have evolved mechanisms to make themselves more appealing to the particular type of pollinator, e.g. brightly colored or scented flowers, nectar, and appealing shapes and patterns. These plant-animal relationships are often mutually beneficial because of the food source provided in exchange for pollination.

<span class="mw-page-title-main">Nectar</span> Sugar-rich liquid produced by many flowering plants, that attracts pollinators and insects

Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide herbivore protection. Common nectar-consuming pollinators include mosquitoes, hoverflies, wasps, bees, butterflies and moths, hummingbirds, honeyeaters and bats. Nectar plays a crucial role in the foraging economics and evolution of nectar-eating species; for example, nectar foraging behavior is largely responsible for the divergent evolution of the African honey bee, A. m. scutellata and the western honey bee.

<span class="mw-page-title-main">Nectarivore</span> Animal in which nectar is a main source of nutrition in their diet

In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants.

<span class="mw-page-title-main">Ornithophily</span> Pollination by birds

Ornithophily or bird pollination is the pollination of flowering plants by birds. This sometimes coevolutionary association is derived from insect pollination (entomophily) and is particularly well developed in some parts of the world, especially in the tropics, Southern Africa, and on some island chains. The association involves several distinctive plant adaptations forming a "pollination syndrome". The plants typically have colourful, often red, flowers with long tubular structures holding ample nectar and orientations of the stamen and stigma that ensure contact with the pollinator. Birds involved in ornithophily tend to be specialist nectarivores with brushy tongues and long bills, that are either capable of hovering flight or light enough to perch on the flower structures.

<i>Habropoda laboriosa</i> Species of bee

Habropoda laboriosa, the southeastern blueberry bee, is a bee in the family Apidae. It is native to the eastern United States. It is regarded as the most efficient pollinator of southern rabbiteye blueberries, because the flowers require buzz pollination, and H. laboriosa is one of the few bees that exhibit this behavior. It is active for only a few weeks of the year, while the blueberries are in flower during early spring, when the temperature is warm and humid. H. laboriosa are solitary bees that live alone but nest in close proximity with other nests of their species. They have similar features to bumble bees, but they are smaller in size compared to them. H. laboriosa are arthropods so they have segmented bodies that are composed of the head, thorax, and abdomen.

<span class="mw-page-title-main">Nectar robbing</span> Foraging behavior

Nectar robbing is a foraging behavior used by some organisms that feed on floral nectar, carried out by feeding from holes bitten in flowers, rather than by entering through the flowers' natural openings. "Nectar robbers" usually feed in this way, avoiding contact with the floral reproductive structures, and therefore do not facilitate plant reproduction via pollination. Because many species that act as pollinators also act as nectar robbers, nectar robbing is considered to be a form of exploitation of plant-pollinator mutualism. While there is variation in the dependency on nectar for robber species, most species rob facultatively.

<span class="mw-page-title-main">Western honey bee</span> European honey bee

The western honey bee or European honey bee is the most common of the 7–12 species of honey bees worldwide. The genus name Apis is Latin for "bee", and mellifera is the Latin for "honey-bearing" or "honey carrying", referring to the species' production of honey.

<span class="mw-page-title-main">Hearing</span> Sensory perception of sound by living organisms

Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science.

The cochlear amplifier is a positive feedback mechanism within the cochlea that provides acute sensitivity in the mammalian auditory system. The main component of the cochlear amplifier is the outer hair cell (OHC) which increases the amplitude and frequency selectivity of sound vibrations using electromechanical feedback.

<span class="mw-page-title-main">Floral scent</span>

Floral scent, or flower scent, is composed of all the volatile organic compounds (VOCs), or aroma compounds, emitted by floral tissue. Other names for floral scent include, aroma, fragrance, floral odour or perfume. Flower scent of most flowering plant species encompasses a diversity of VOCs, sometimes up to several hundred different compounds. The primary functions of floral scent are to deter herbivores and especially folivorous insects, and to attract pollinators. Floral scent is one of the most important communication channels mediating plant-pollinator interactions, along with visual cues.

<span class="mw-page-title-main">Biotremology</span>

Biotremology is the study of production, dispersion and reception of mechanical vibrations by organisms, and their effect on behavior. This involves neurophysiological and anatomical basis of vibration production and detection, and relation of vibrations to the medium they disperse through. Vibrations can represent either signals used in vibrational (seismic) communication or inadvertent cues used, for example, in locating prey. In almost all known cases, they are transmitted as surface waves along the boundary of a medium, i.e. Rayleigh waves or bending waves. While most attention is directed towards the role of vibrations in animal behavior, plants actively respond to sounds and vibrations as well, so this subject is shared with plant bioacoustics. Other groups of organisms are also postulated to either actively produce or at least use vibrations to sense their environment, but those are currently far less studied.

In plant biology, plant memory describes the ability of a plant to retain information from experienced stimuli and respond at a later time. For example, some plants have been observed to raise their leaves synchronously with the rising of the sun. Other plants produce new leaves in the spring after overwintering. Many experiments have been conducted into a plant's capacity for memory, including sensory, short-term, and long-term. The most basic learning and memory functions in animals have been observed in some plant species, and it has been proposed that the development of these basic memory mechanisms may have developed in an early organismal ancestor.

Phonotropism is the growth of organisms in response to sound stimuli. Root phonotropism is when the roots of a plant grow towards or away in response to a sound source. Acoustic cues are detected by the plant as sound waves which then induces a mechanistic response that changes plant behavior. Plants adapt to respond to external stimuli because of their sessile nature, and it is evolutionarily plausible that these organisms have adapted to take advantage of these inputs to help foraging behavior or defense mechanisms. Arabidopsis roots have been observed to gravitate towards sounds of flowing water, while caterpillar feeding vibrations alone are sufficient to alter plant defense hormones and volatile emissions in Arabidopsis leaves.

<span class="mw-page-title-main">UV coloration in flowers</span> Natural phenomenon

UV coloration is a natural phenomenon that leads to unique interactions between organisms that have evolved the ability to perceive these wavelengths of light. It serves as one method to attract pollinators to the flower along with scent, shape, and nectar quality. Flowers are known for their range of visible colors that humans can see with their eyes and observe an array of different shades and patterns. The naked eye cannot see the ultraviolet coloration many flowers employ to bring attention to themselves. By either reflecting or absorbing UV light waves, flowers are able to communicate with pollinators. This allows plants that may require an animal pollinator to stand out from other flowers or distinguish where their flowers are in a muddied background of other plant parts. For the plant, it is important to share and receive pollen so they can reproduce, maintain their ecological role, and guide the evolutionary history of the population.

References

  1. ↑ Gagliano M, Renton M, Duvdevani N, Timmins M, Mancuso S (2012). "Out of sight but not out of mind: alternative means of communication in plants". PLOS ONE. 7 (5): e37382. Bibcode:2012PLoSO...737382G. doi: 10.1371/journal.pone.0037382 . PMC   3358309 . PMID   22629387.
  2. ↑ Smith H (October 2000). "Phytochromes and light signal perception by plants--an emerging synthesis". Nature. 407 (6804): 585–91. Bibcode:2000Natur.407..585S. doi:10.1038/35036500. PMID   11034200. S2CID   4418526.
  3. ↑ Karban R, Shiojiri K (June 2009). "Self-recognition affects plant communication and defense". Ecology Letters. 12 (6): 502–6. doi:10.1111/j.1461-0248.2009.01313.x. PMC   3014537 . PMID   19392712.
  4. ↑ Pare PW, Tumlinson JH (October 1999). "Plant volatiles as a defense against insect herbivores". Plant Physiology. 121 (2): 325–32. doi:10.1104/pp.121.2.325. PMC   1539229 . PMID   10517823.
  5. ↑ Gagliano M (July 2013). "Green symphonies: a call for studies on acoustic communication in plants". Behavioral Ecology. 24 (4): 789–796. doi:10.1093/beheco/ars206. PMC   3677178 . PMID   23754865.
  6. 1 2 3 Gagliano M, Mancuso S, Robert D (June 2012). "Towards understanding plant bioacoustics". Trends in Plant Science. 17 (6): 323–5. doi:10.1016/j.tplants.2012.03.002. PMID   22445066.
  7. ↑ "The flowering of plant bioacoustics: how and why". ... For example, some 20000 species use buzz pollination ...
  8. ↑ Buchmann SL, Hurley JP (June 1978). "A biophysical model for buzz pollination in angiosperms". Journal of Theoretical Biology. 72 (4): 639–57. Bibcode:1978JThBi..72..639B. doi:10.1016/0022-5193(78)90277-1. PMID   672247.
  9. ↑ "Plants Profile for Oenothera drummondii (beach evening primrose)". plants.usda.gov. Retrieved 2019-06-02.
  10. 1 2 3 4 5 6 Veits M, Khait I, Obolski U, Zinger E, Boonman A, Goldshtein A, Saban K, Ben-Dor U, Estlein P, Kabat A, Peretz D (2018-12-28). "Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration.: Supplementary Data". bioRxiv. doi: 10.1101/507319 .
  11. ↑ Appel HM, Cocroft RB (August 2014). "Plants respond to leaf vibrations caused by insect herbivore chewing". Oecologia. 175 (4): 1257–66. Bibcode:2014Oecol.175.1257A. doi:10.1007/s00442-014-2995-6. PMC   4102826 . PMID   24985883.
  12. ↑ Walley JW, Coughlan S, Hudson ME, Covington MF, Kaspi R, Banu G, Harmer SL, Dehesh K (October 2007). "Mechanical stress induces biotic and abiotic stress responses via a novel cis-element". PLOS Genetics. 3 (10): 1800–12. doi: 10.1371/journal.pgen.0030172 . PMC   2039767 . PMID   17953483.
  13. ↑ "Pollinator Syndromes". www.fs.fed.us. Retrieved 2019-06-02.
  14. ↑ Laschimke R, Burger M, Vallen H (October 2006). "Acoustic emission analysis and experiments with physical model systems reveal a peculiar nature of the xylem tension". Journal of Plant Physiology. 163 (10): 996–1007. doi:10.1016/j.jplph.2006.05.004. PMID   16872717.
  15. ↑ Perks MP, Irvine J, Grace J (January 2004). "Xylem acoustic signals from mature Pinus sylvestris during an extended drought" (PDF). Annals of Forest Science. 61 (1): 1–8. doi: 10.1051/forest:2003079 .
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