Pappus (botany)

Not to be confused with Glossary of botanical terms § coma.

This article is about a flower structure. For the mathematician, see Pappus of Alexandria.

"Pappi" redirects here. For the 1934 German film, see Pappi (film).

In Asteraceae, the pappus is the modified calyx,^[1] the part of an individual floret, that surrounds the base of the corolla tube in flower. It functions as a dispersal mechanism for the achenes that contain the seeds.

The pappus-clad fruits that make up the familiar "dandelion clock" being dispersed by the wind (family Asteraceae)

Bidens frondosa achenes with barbed pappus

In Asteraceae, the pappus may be composed of bristles (sometimes feathery), awns, scales, or may be absent, and in some species, is too small to see without magnification. In genera such as Taraxacum or Eupatorium, feathery bristles of the pappus function as a "parachute" which enables the seed to be carried by the wind.^[2] In genera such as Bidens the pappus has hooks that function in mechanical dispersal.

The name derives from the Ancient Greek word pappos, Latin pappus, meaning "old man", so used for a plant (assumed to be an Erigeron species) having bristles and also for the woolly, hairy seed of certain plants.

The pappus of the dandelion plays a vital role in the wind-aided dispersal of its seeds. By creating a separated vortex ring in its wake, the flight of the pappus is stabilized and more lift and drag are produced.^[3][4] The pappus also has the property of being able to change its morphology in the presence of moisture in various ways that aid germination. The change of shape can adjust the rate of abscission, allowing increased or decreased germination depending on the favorability of conditions.^[5][6]

Biomimicry

The pappus of the dandelion has been studied and reproduced for a variety of applications. It has the ability to retain about 100 times its weight in water and pappus-inspired mechanisms have been proposed and fabricated which would allow highly efficient and specialized liquid transport.^[7] Another application of the pappus is in the use of minute airflow detection around walls which is important for measuring small fluctuations in airflow in neonatal incubators or to measure low velocity airflow in heating and ventilation systems.^[8]

References

1. Wunderlin, Richard P.; Hansen, Bruce F. (2011). Guide to the vascular plants of Florida (3rd ed.). Gainesville (Fla.): University press of Florida. p. 640. ISBN 978-0-8130-3543-7.
2. "Composite flowers".
3. Cummins, Cathal; Seale, Madeleine; Macente, Alice; Certini, Daniele; Mastropaolo, Enrico; Viola, Ignazio Maria; Nakayama, Naomi (2018). "A separated vortex ring underlies the flight of the dandelion" (PDF). Nature. 562 (7727): 414–418. Bibcode:2018Natur.562..414C. doi:10.1038/s41586-018-0604-2. ISSN 0028-0836. PMID 30333579. S2CID 52988814.
4. Ledda, P. G.; Siconolfi, L.; Viola, F.; Camarri, S.; Gallaire, F. (2019-07-02). "Flow dynamics of a dandelion pappus: A linear stability approach". Physical Review Fluids. 4 (7): 071901. Bibcode:2019PhRvF...4g1901L. doi:10.1103/physrevfluids.4.071901. hdl:11568/998044. ISSN 2469-990X. S2CID 198429309.
5. Greene, David F. (2005). "The Role of Abscission in Long-Distance Seed Dispersal by the Wind". Ecology. 86 (11): 3105–3110. doi:10.1890/04-1430. ISSN 0012-9658.
6. Seale, Madeleine; Zhdanov, Oleksandr; Cummins, Cathal; Kroll, Erika; Blatt, Michael R; Zare-Behtash, Hossein; Busse, Angela; Mastropaolo, Enrico; Viola, Ignazio Maria (2019-02-07), Moisture-dependent morphing tunes the dispersal of dandelion diaspores, doi:10.1101/542696, hdl:10044/1/102018
7. Meng, Qingan; Wang, Qianbin; Liu, Huan; Jiang, Lei (2014). "A bio-inspired flexible fiber array with an open radial geometry for highly efficient liquid transfer". NPG Asia Materials. 6 (9): e125. doi:10.1038/am.2014.70. ISSN 1884-4049.
8. Bruecker, Christoph H.; Mikulich, Vladimir (2017-06-28). "Sensing of minute airflow motions near walls using pappus-type nature-inspired sensors". PLOS ONE. 12 (6): e0179253. Bibcode:2017PLoSO..1279253B. doi:10.1371/journal.pone.0179253. ISSN 1932-6203. PMC 5489159. PMID 28658272.

External links

• Asteraceae morphology
• Composite flowers
• Biomimetics