Good day, dear Take in Mind readers! Don’t be confused by the title of this post: It’s not about alien visitors or Shrek the Ogre, and of course, we’re not going to discuss Greenpeace activities.
Everything is much more simple and interesting. We will talk about the acoustic ability of plants. The following fact came to us as a surprise: Pp to now, the question of whether plants can sense natural sounds or not was almost not investigated. That’s even more surprising if we take into account all the reasons to study that question. For example, recent studies demonstrated that artificial acoustic stimuli may affect the growth rate of plants, although, the changes were very slow (lasting hours or even days); Plant tissues have been shown to vibrate to a range of sounds, and, there is a long discussion in the scientific literature about the possible plants’ mechanisms to use signals other than color, smell, and shape for insect attractions (for example, during pollination).
In their recent study, an Israeli research group headed by Prof. Lilach Hadany showed that Oenothera drummondii flowers, exposed to flying bee sounds or to synthetic acoustic signals at similar frequencies, produce sweeter nectar (approximately 20% increase) within the following three minutes [1].
Moreover, the researchers found that the flowers “answered” (more accurately, vibrated) in response to these sounds, suggesting a probable mechanism where the flower serves as an auditory sensory organ. Both the vibration and the nectar response were frequency‐specific: the flowers responded and vibrated to pollinator sounds, but not to higher frequency sound.
In the article, as well as in their reply to comments [2], the authors discussed numerous scientific and applied aspects of their discovery. Why does the production of sweeter nectar occur within three minutes (and not, for example, ten minutes), and can this be related to the pollinator’s move between nearby flowers? How does a plant “tune” itself exactly to those acoustic frequencies that are produced by the insects’ flapping wings? Why does the sugar concentration in nectar elevate by 20%, and not two-three times more?
We do not want to prevent you from the pleasure of reading the author’s full answers to these and other questions. We will provide the original explanation only to the following question: why does the quality of nectar (i.e., the sugar concentration) and not other parameters change as a result of the “communication” with a bee?
Increased sugar concentration can enhance at least two behavioral processes in the pollinators: (a) prolongation of the pollinator’s visit (how long it will stay) and (b) facilitation of the pollinator constancy (in other words, the number of visits in the future).
This is also known that a rise in the nectar’s sugar concentration attracts more pollinators and also increases the visit duration. Moreover, insects quickly learn to visit more “beneficial” plants and their surrounding after such a pleasant and useful visit, and this, in turn, may benefit also the plant itself.
In other words, such a “businessflower” can increase both the visit’s prolongation and the pollinator’s “loyalty”, while saving energy by producing relatively low sugar nectar when there is no pollinator nearby.
By the way, an explanation of the fact that sugar content is up for only 20% may be that having too high sugar concentration can result in too viscous nectar for some pollinators. Bees are capable of perceiving differences in sugar concentration, as small as 1‐3%, therefore, 20% sweeter nectar may be accepted by the insects as a “super-delicious” one.
If this mechanism is not a kind of some evolutionary phenomenon for only the Oenothera drummondii species, this work may become the basis for completely new approaches in botany, ecology, and agriculture. Plant response to sound may allow bidirectional feedback between pollinators and plants, which can improve the synchronization between them, lowering nectar waste and potentially improving the efficiency of pollination. These advantages can be diminished in very noisy environments, suggesting possible sensitivity of pollination to external noises (for example, if the field or garden is close to any industrial area or road). Finally, plants’ ability to sense sounds has implications way beyond pollination: plants could potentially sense and respond to sounds of other animals, and even possibly of other plants.
P.S. Maybe John Ronald Tolkien or John Wyndham with their Ents and Triffids did not go so far in their imagination?
[1] Veits M, Khait I, Obolski U, et al. Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration. Ecol Lett. 2019;22(9):1483-1492. doi:10.1111/ele.13331 – https://pubmed.ncbi.nlm.nih.gov/31286633/
[2] Goldshtein A, Veits M, Khait I, et al. Plants’ ability to sense and respond to airborne sound is likely to be adaptive: reply to comment by Pyke et al. Ecol Lett. 2020;23(9):1423-1425. doi:10.1111/ele.13514 – https://pubmed.ncbi.nlm.nih.gov/32578320/
Featured image by Jaesung An from Pixabay.
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