Biology:Smell of freshly cut grass

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Short description: Odour released when grass is damaged
The release of green leaf volatiles following the cutting of a lawn is responsible for the odour of freshly cut grass.

The smell of freshly cut grass is an odour caused by green leaf volatiles (GLVs) released when it is damaged. Mechanical damage to grass from activities such as lawnmowing results in the release of cis-3-hexenal and other compounds that contribute to a grassy or "green" smell. cis-3-Hexenal has a low odour detection threshold that humans can perceive at concentrations as low as 0.25 parts per billion.

The GLVs responsible for the smell of freshly cut grass play a role in plant communication and plant defence against herbivory, functioning as a distress signal warning other plants of imminent danger and, in some instances, as a way to attract predators of grass-eating insects. For humans, the smell of freshly cut grass is connected through olfactory memory to past experiences involving the odour and may evoke nostalgia, eliciting associations with spring or summer.

Chemical composition

When grass is cut or damaged, lipoxygenase enzymes begin a breakdown of membranes in the plant's cells, producing linoleic and linolenic acids. Exposure to oxygen leads to the formation of cis-3-hexenal, which rapidly breaks down to cis-3-hexenol (leaf alcohol) and (E)-2-hexenal (leaf aldehyde). These green leaf volatiles (GLVs) are a combination of alcohols, aldehydes, and esters. The oxygenated hydrocarbons cause a "green" odour.[1]

The smell of freshly cut grass is evident immediately after mechanical damage, such as that done by mowing the lawn.

The main compound responsible for the smell of freshly cut grass is cis-3-hexenal. It has a low odour detection threshold that humans can perceive at concentrations as low as 0.25 parts per billion. The compound is highly unstable and breaks down into (E)-2-hexenal (leaf aldehyde),[2] which may account for why the smell is said to fade rapidly.[3]

The composition of green leaf volatiles produced by cut grasses varies. In lawns, hayfields, and meadows, other plant species such as clover may be present. Sweet clover may impart a haylike or vanilla-like scent due to the presence of coumarin.[4]

While grasses release hydrocarbons passively and in response to strong sunlight, when cut or damaged, the emissions may increase by a factor of 180.[5] A second release of volatile organic compounds occurs after grass has been cut. An experiment analysing cut red fescue grass (Festuca rubra) and white clover (Trifolium repens) found prolonged releases of (Z)-3-hexenal, (Z)-3-hexenol, and hexenyl acetate. The emissions also included acetaldehyde, acetone, butanone, methanol, and possibly formaldehyde.[6] Highly reactive hydrocarbons released by cut grass combine with gases such as nitrogen oxides and exacerbate photochemical smog and urban air pollution by contributing to the formation of aerosols and ozone.[7][8] In cities, lawnmowing can account for 10% of the total hydrocarbon release into the atmosphere.[5]

Biological role

Green leaf volatiles (GLVs) are volatile organic compounds that play an important role in plant communication and plant defence against herbivory. The release of GLVs functions as a distress signal to other plants that danger is imminent. GLVs may also attract the predators of grass-eating insects, with insect and bird species having been shown to respond to GLV releases by certain injured plants.[9][10]

Human perception and olfactory memory

The smell of freshly cut grass may evoke associations with chores.

For humans, the smell of freshly cut grass is connected through olfactory memory[11] to experiences related to lawns, lawn mowers,[12] or haying. The smell may evoke nostalgia, eliciting associations with spring or summer,[13] parklands, golf courses, or preparations for sporting events.[14][15]

The smell of freshly cut grass is described as a leafy or "green" scent.[1][16] Positive associations to GLVs released by grasses may be due to their similarity to the GLVs released by edible plants such as vegetables when they are ripe.[17]

The smell of freshly cut grass has been described as "uplifting",[18] and behavioral studies have shown that the smell has a "healing effect on psychological damage caused by stress".[16] Hexanal, which resembles the smell of freshly cut grass, can increase interpersonal trust.[19]

A trademark case before the Office for Harmonization in the Internal Market addressed an attempt to secure a trademark for the smell of freshly cut grass for use with tennis balls. An appeals board found that "the smell of freshly cut grass is a distinct smell which everyone immediately recognizes from experience. For many, the scent or fragrance of freshly cut grass reminds them of spring or summer, manicured lawns or playing fields, or other such pleasant experiences."[20]

Happiness in childhood may have a bearing on the subjective experience of the smell. In one study, people born before 1960 recalled a happy childhood when describing the smell of freshly cut grass, while those born after 1960 described unhappy childhoods. Subjects born earlier had pride in the responsibility of cutting grass while those born later associated the smell with chores.[21]

About 12% of humans have difficulty smelling cis-3-hexen-1-ol.[22] A pair of single-nucleotide polymorphisms in the OR2J3 gene strongly reduce sensitivity to the odorant cis-3-hexen-1-ol, which has a "cut grass" smell.[23]

The toxic, colourless gas phosgene smells like freshly cut grass.[24] The Mauzac-based sparkling wine Blanquette de Limoux has aromas of fresh cut grass.[25]

Use in industry

The chemicals responsible for the smell of freshly cut grass are used as aroma compounds by the perfume industry. Hexanal and related compounds are used by the food industry in recreating fruit and vegetable flavours. The yearly production of cis-3-Hexen-1-ol is about 30 tonnes. The compound, which has the smell of freshly cut grass, is naturally present in tomatoes, kiwifruit, olive oil, and green tea.[26]

See also

References

  1. ↑ 1.0 1.1 Soniak, Matt (1 May 2012). "That "Fresh Cut Grass" Smell Is a Distress Signal". Mental Floss. https://www.mentalfloss.com/article/30573/what-causes-fresh-cut-grass-smell. 
  2. ↑ Kirstine, Wayne; Galbally, Ian; Ye, Yuerong; Hooper, Martin (20 May 1998). "Emissions of volatile organic compounds (primarily oxygenated species) from pasture". Journal of Geophysical Research: Atmospheres 103 (D9): 10605–10619. doi:10.1029/97JD03753. Bibcode: 1998JGR...10310605K. 
  3. ↑ Stewart, Jude (2021) (in en). Revelations in Air: A Guidebook to Smell. Penguin. p. 38. ISBN 978-0-525-50760-4. https://books.google.com/books?id=NyIfEAAAQBAJ&dq=fresh+cut+grass+smell&pg=PA38. Retrieved 2023-07-29. 
  4. ↑ Mcgee, Harold (2020) (in en). Nose Dive: A Field Guide to the World's Smells. John Murray Press. ISBN 978-1-4447-2215-4. https://books.google.com/books?id=2p9nCwAAQBAJ&dq=smell+cut+grass&pg=PT169. Retrieved 2023-07-29. 
  5. ↑ 5.0 5.1 Anderson, Ian (9 May 1998). "Keep off the grass". New Scientist. https://www.newscientist.com/article/mg15821331-700-keep-off-the-grass/. 
  6. ↑ de Gouw, Joost A.; Howard, Carleton J.; Custer, Thomas G.; Fall, Ray (1 April 1999). "Emissions of volatile organic compounds from cut grass and clover are enhanced during the drying process". Geophysical Research Letters 26 (7): 811–814. doi:10.1029/1999GL900076. Bibcode: 1999GeoRL..26..811D. 
  7. ↑ "Keep Off The Grass – Reduce Air Pollution" (in en). ScienceDaily. 20 April 1998. https://www.sciencedaily.com/releases/1998/04/980420003419.htm. 
  8. ↑ Brilli, Federico; Hörtnagl, Lukas; Bamberger, Ines (3 April 2012). "Qualitative and Quantitative Characterization of Volatile Organic Compound Emissions from Cut Grass". Environmental Science & Technology 46 (7): 3859–3865. doi:10.1021/es204025y. PMID 22409212. Bibcode: 2012EnST...46.3859B. 
  9. ↑ Moser, Keith (2022) (in en). Contemporary French Environmental Thought in the Post-COVID-19 Era. Springer Nature. p. 180. ISBN 978-3-030-96129-9. https://books.google.com/books?id=r0FpEAAAQBAJ&dq=fresh+cut+grass+smell&pg=PA180. Retrieved 2023-07-29. 
  10. ↑ Wikelski, Martin; Quetting, Michael; Cheng, Yachang (18 June 2021). "Smell of green leaf volatiles attracts white storks to freshly cut meadows" (in en). Scientific Reports 11 (1): 12912. doi:10.1038/s41598-021-92073-7. PMID 34145327. Bibcode: 2021NatSR..1112912W. 
  11. ↑ Baldwin, Jennifer (2016) (in en). Sensing Sacred: Exploring the Human Senses in Practical Theology and Pastoral Care. Rowman & Littlefield. p. 31. ISBN 978-1-4985-3124-5. https://books.google.com/books?id=Oj_TDAAAQBAJ&dq=fresh+cut+grass+%22olfactory+memory%22&pg=PA31. Retrieved 2023-08-08. 
  12. ↑ Herz, R. S. (1 March 2004). "A Naturalistic Analysis of Autobiographical Memories Triggered by Olfactory Visual and Auditory Stimuli". Chemical Senses 29 (3): 217–224. doi:10.1093/chemse/bjh025. PMID 15047596. https://academic.oup.com/chemse/article/29/3/217/321318. Retrieved 8 August 2023. 
  13. ↑ Stall-Paquet, Caitlin (12 May 2022). "The case for leaving the perfectly manicured lawn behind". CBC. https://www.cbc.ca/life/home/the-case-for-leaving-the-perfectly-manicured-lawn-behind-1.6449477. 
  14. ↑ Brkic, Belma R.; Chalmers, Alan; Boulanger, Kevin (April 2009). "Cross-modal affects of smell on the real-time rendering of grass". Proceedings of the 25th Spring Conference on Computer Graphics. pp. 161–166. doi:10.1145/1980462.1980494. ISBN 9781450307697. https://www.researchgate.net/publication/234818895. Retrieved 2023-08-08. 
  15. ↑ Verbeek, Caro; van Campen, Cretien (July 2013). "Inhaling Memories: Smell and Taste Memories in Art, Science, and Practice". The Senses and Society 8 (2): 133–148. doi:10.2752/174589313X13589681980696. 
  16. ↑ 16.0 16.1 Landry, Charles (2012) (in en). The Art of City Making. Routledge. p. 62. ISBN 978-1-136-55496-4. https://books.google.com/books?id=IKlZthMzjTMC&dq=smell+of+cut+grass&pg=PA62. Retrieved 2023-07-29. 
  17. ↑ Grunbaum, Mara (5 May 2019). "Why Does Freshly Cut Grass Smell So Nice?" (in en). Live Science. https://www.livescience.com/65400-why-freshly-cut-grass-smells-good.html. 
  18. ↑ Farmer, Edward E. (2014) (in en). Leaf Defence. OUP Oxford. ISBN 978-0-19-165120-5. https://books.google.com/books?id=dWBiAwAAQBAJ&dq=fresh+cut+grass+smell&pg=PT157. Retrieved 2023-07-29. 
  19. ↑ van Nieuwenburg, Daan; de Groot, Jasper H. B.; Smeets, Monique A. M. (20 August 2019). "The Subtle Signaling Strength of Smells: A Masked Odor Enhances Interpersonal Trust". Frontiers in Psychology 10: 1890. doi:10.3389/fpsyg.2019.01890. PMID 31481913. 
  20. ↑ Freeman, Lee; Peace, A. Graham (2005) (in en). Information Ethics: Privacy and Intellectual Property. Idea Group Inc (IGI). p. 82. ISBN 978-1-59140-492-7. https://books.google.com/books?id=QnoZGkGzpkQC&dq=fresh+cut+grass+smell&pg=PA82. Retrieved 2023-07-29. 
  21. ↑ Hirsch, Alan R. (14 September 2011). "The smell brain" (in en). Neurology. https://n.neurology.org/content/smell-brain. 
  22. ↑ Striedter, Georg F. (2016) (in en). Neurobiology: A Functional Approach. Oxford University Press. p. 180. ISBN 978-0-19-539615-7. https://books.google.com/books?id=AkoACwAAQBAJ&dq=fresh+cut+grass+smell&pg=PA180. Retrieved 2023-07-29. 
  23. ↑ "Genetic variation in the odorant receptor OR2J3 is associated with the ability to detect the "grassy" smelling odor, cis-3-hexen-1-ol". Chemical Senses 37 (7): 585–93. September 2012. doi:10.1093/chemse/bjs049. PMID 22714804. PMC 3408771. https://www.sciencedirect.com/science/article/abs/pii/B9781845695675500204. Retrieved 2023-07-29. 
  24. ↑ (in en) The First Responder's Field Guide to Hazmat and Terrorism Emergency Response. Firebelle Productions. September 2006. p. 9-9. ISBN 978-0-9651516-9-6. https://books.google.com/books?id=gkcDurv6eYEC&dq=fresh+cut+grass+smell&pg=PT289. Retrieved 2023-07-29. 
  25. ↑ Stevenson, Tom (1998). Christie's World Encyclopedia of Champagne & Sparkling Wine. Absolute Press. p. 137. ISBN 978-1-899791-98-9. 
  26. ↑ Newcomb, R.D.; McRae, J.; Ingram, J. (2010). "Genetic variation in taste and odour perception: an emerging science to guide new product development". Consumer-Driven Innovation in Food and Personal Care Products: 570–596. doi:10.1533/9781845699970.5.570. ISBN 9781845695675. 



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