The pappus is the modified calyx, the part of an individual floret, that surrounds the base of the corolla tube in flower heads of the plant family Asteraceae. The term is sometimes used for similar structures present as a wind-dispersal mechanism for seeds of genera in other plant families e.g. in certain genera of the Apocynaceae, although such structures are not derived from the calyx of the flower.
The Asteraceae pappus may be composed of bristles (sometimes feathery), awns, scales, or may be absent. In some species, the pappus is too small to see without magnification. In species such as Dandelion or Eupatorium, feathery bristles of the pappus function as a "parachute" which enables the seed to be carried by the wind. 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. 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.
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. 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.
- "Composite flowers".
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- 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.
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