Pollen

Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower.

{{stack|float=left|File:Coenocytic Tetrad.gif at coenocytic tetrad stage of development observed through oil immersion microscope; the chromosomes of what will become four pollen grains can be seen.]]}}

In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a partially differentiated dermis. As the flower develops, fertile sporogenous cells, the archespore, form within the anther. The sporogenous cells are surrounded by layers of sterile cells that grow into the wall of the pollen sac. Some of the cells grow into nutritive cells that supply nutrition for the microspores that form by meiotic division from the sporogenous cells. The archespore cells divide by mitosis and differentiate to form pollen mother cells (microsporocyte, meiocyte).

In a process called microsporogenesis, four haploid microspores are produced from each diploid pollen mother cell, after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins. The callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is what is preserved in the fossil record.

Two basic types of microsporogenesis are recognised, simultaneous and successive. In simultaneous microsporogenesis meiotic steps I and II are completed before cytokinesis, whereas in successive microsporogenesis cytokinesis follows. While there may be a continuum with intermediate forms, the type of microsporogenesis has systematic significance. The predominant form amongst the monocots is successive, but there are important exceptions.{{cite journal |last1=Furness|first1=Carol A. |last2=Rudall|first2=Paula J.|author-link2=Paula Rudall|title=Pollen and anther characters in monocot systematics|journal=Grana|date=January 2001|volume=40|issue=1–2|pages=17–25|doi=10.1080/00173130152591840|doi-access=free|bibcode=2001Grana..40...17F }}

During microgametogenesis, the unicellular microspores undergo mitosis and develop into mature microgametophytes containing the gametes.{{Cite web |url=http://www2.le.ac.uk/departments/biology/people/twell/lab/pollenis/development |title=Pollen Development — University of Leicester |access-date=2013-12-12 |archive-date=2014-10-06 |archive-url=https://web.archive.org/web/20141006193005/http://www2.le.ac.uk/departments/biology/people/twell/lab/pollenis/development/ |url-status=dead }} In some flowering plants,{{which|date=February 2017}} germination of the pollen grain may begin even before it leaves the microsporangium, with the generative cell forming the two sperm cells.

File:Tulip Stamen Tip.jpg with many grains of pollen]]

File:Cactus flower pollen.jpg

File:Jasper - Pollen storm - 20140624B.jpg]]

Except in the case of some submerged aquatic plants, the mature pollen grain has a double wall. The vegetative and generative cells are surrounded by a thin delicate wall of unaltered cellulose called the endospore or intine, and a tough resistant outer cuticularized wall composed largely of sporopollenin called the exospore or exine. The exine often bears spines or warts, or is variously sculptured, and the character of the markings is often of value for identifying genus, species, or even cultivar or individual.

The spines may be less than a micron in length (spinulus, plural spinuli) referred to as spinulose (scabrate), or longer than a micron (echina, echinae) referred to as echinate. Various terms also describe the sculpturing such as reticulate, a net like appearance consisting of elements (murus, muri) separated from each other by a lumen (plural lumina). These reticulations may also be referred to as brochi.

The pollen wall protects the sperm while the pollen grain is moving from the anther to the stigma; it protects the vital genetic material from drying out and solar radiation. The pollen grain surface is covered with waxes and proteins, which are held in place by structures called sculpture elements on the surface of the grain. The outer pollen wall, which prevents the pollen grain from shrinking and crushing the genetic material during desiccation,{{citation needed|date=June 2022}} is composed of two layers. These two layers are the tectum and the foot layer, which is just above the intine. The tectum and foot layer are separated by a region called the columella, which is composed of strengthening rods. The outer wall is constructed with a resistant biopolymer called sporopollenin.

Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness.{{Cite journal|last1=Furness|first1=Carol A.|last2=Rudall|first2=Paula J.|date=2004-03-01|title=Pollen aperture evolution--a crucial factor for eudicot success?|journal=Trends in Plant Science|volume=9|issue=3|pages=154–158|doi=10.1016/j.tplants.2004.01.001|pmid=15003239|citeseerx=10.1.1.462.5084}} They allow shrinking and swelling of the grain caused by changes in moisture content. The process of shrinking the grain is called harmomegathy.{{cite journal |last1=Katifori |first1=Eleni |last2=Alben |first2=Silas |last3=Cerda |first3=Enrique |last4=Nelson |first4=David R. |last5=Dumais |first5=Jacques |title=Foldable structures and the natural design of pollen grains |journal=Proceedings of the National Academy of Sciences |date=27 April 2010 |volume=107 |issue=17 |pages=7635–7639 |doi=10.1073/pnas.0911223107 |pmid=20404200 |pmc=2867878 |bibcode=2010PNAS..107.7635K |doi-access=free}} Elongated apertures or furrows in the pollen grain are called colpi (singular: colpus) or sulci (singular: sulcus). Apertures that are more circular are called pores. Colpi, sulci and pores are major features in the identification of classes of pollen.{{cite web|url=http://www.geo.arizona.edu/palynology/ppapertr.html|author=Davis, Owen|title=Aperture|work=geo.arizona.edu|access-date=2009-02-16|archive-url=https://web.archive.org/web/20090203035127/http://www.geo.arizona.edu/palynology/ppapertr.html|archive-date=2009-02-03}} Pollen may be referred to as inaperturate (apertures absent) or aperturate (apertures present).

The aperture may have a lid (operculum), hence is described as operculate.{{cite journal|last1=Furness|first1=Carol A.|last2=Rudall|first2=Paula J.|author-link2=Paula Rudall|title=Apertures with Lids: Distribution and Significance of Operculate Pollen in Monocotyledons|journal=International Journal of Plant Sciences|date=November 2003|volume=164|issue=6|pages=835–854|doi=10.1086/378656|bibcode=2003IJPlS.164..835F |s2cid=84766627}} However the term inaperturate covers a wide range of morphological types, such as functionally inaperturate (cryptoaperturate) and omniaperturate. Inaperaturate pollen grains often have thin walls, which facilitates pollen tube germination at any position. Terms such as uniaperturate and triaperturate refer to the number of apertures present (one and three respectively). Spiraperturate refers to one or more apertures being spirally shaped.

The orientation of furrows (relative to the original tetrad of microspores) classifies the pollen as sulcate or colpate. Sulcate pollen has a furrow across the middle of what was the outer face when the pollen grain was in its tetrad. If the pollen has only a single sulcus, it is described as monosulcate, has two sulci, as bisulcate, or more, as polysulcate.{{cite book |chapter-url=https://books.google.com/books?id=dj8KRImgyf4C&pg=PA453 |first1=Michael G. |last1=Simpson |title=Plant Systematics |chapter=Palynology|pages=453–464|publisher=Academic Press |year=2011 |isbn=978-0-08-051404-8 |access-date=6 January 2014}}{{cite book|chapter-url=https://books.google.com/books?id=In_Lv8iMt24C&pg=142|page=142|chapter=Palynology|access-date=23 January 2014|title=Plant Systematics: An Integrated Approach |isbn=9781578083510|last1=Singh|first1=Gurcharan|date=2004|publisher=Science Publishers }} Colpate pollen has furrows other than across the middle of the outer faces, and similarly may be described as polycolpate if more than two. Syncolpate pollen grains have two or more colpi that are fused at the ends.{{sfn|Kaltenrieder|von Ballmoos |2003}}{{Cite journal| author=Sporne, Kenneth R. | year=1972 | title=Some Observations on the Evolution of Pollen Types in Dicotyledons | journal=New Phytologist | volume= 71 | issue=1 | pages=181–185 | doi=10.1111/j.1469-8137.1972.tb04826.x| doi-access=free| bibcode=1972NewPh..71..181S }} Eudicots have pollen with three colpi (tricolpate) or with shapes that are evolutionarily derived from tricolpate pollen.{{Cite journal|author1=Judd, Walter S. |author2=Olmstead, Richard G. |name-list-style=amp |year = 2004|title = A survey of tricolpate (eudicot) phylogenetic relationships|journal = American Journal of Botany| volume = 91|pages = 1627–1644|doi = 10.3732/ajb.91.10.1627|pmid=21652313|issue = 10|doi-access = free}} The evolutionary trend in plants has been from monosulcate to polycolpate or polyporate pollen.

Additionally, gymnosperm pollen grains often have air bladders, or vesicles, called sacci. The sacci are not actually balloons, but are sponge-like, and increase the buoyancy of the pollen grain and help keep it aloft in the wind, as most gymnosperms are anemophilous. Pollen can be monosaccate, (containing one saccus) or bisaccate (containing two sacci). Modern pine, spruce, and yellowwood trees all produce saccate pollen.{{Cite book |title=Paleopalynology |author=Traverse, Alfred |date=1988 |publisher=Unwin Hyman |isbn=978-0045610013 |oclc=17674795}}

{{Main article|Pollination}}

File:Apis mellifera flying.jpg carrying pollen in a pollen basket back to the hive]]

File:Episyrphus balteatus - head close-up (aka).jpg, pollen on its face and legs, sitting on a rockrose.]]

File:Diadasia Bee Straddles Cactus Flower Carpels close-up.jpg bee straddles flower carpels while visiting yellow Opuntia engelmannii cactus ]]

The transfer of pollen grains to the female reproductive structure (pistil in angiosperms) is called pollination. Pollen transfer is frequently portrayed as a sequential process that begins with placement on the vector, moves through travel, and ends with deposition.{{Cite journal |last1=Minnaar |first1=Corneile |last2=Anderson |first2=Bruce |last3=de Jager |first3=Marinus L |last4=Karron |first4=Jeffrey D |date=2019-01-23 |title=Plant–pollinator interactions along the pathway to paternity |url=https://academic.oup.com/aob/article/123/2/225/5232516 |journal=Annals of Botany |language=en |volume=123 |issue=2 |pages=225–245 |doi=10.1093/aob/mcy167 |issn=0305-7364 |pmc=6344347 |pmid=30535041}} This transfer can be mediated by the wind, in which case the plant is described as anemophilous (literally wind-loving). Anemophilous plants typically produce great quantities of very lightweight pollen grains, sometimes with air-sacs.

Non-flowering seed plants (e.g., pine trees) are characteristically anemophilous. Anemophilous flowering plants generally have inconspicuous flowers. Entomophilous (literally insect-loving) plants produce pollen that is relatively heavy, sticky and protein-rich, for dispersal by insect pollinators attracted to their flowers. Many insects and some mites are specialized to feed on pollen, and are called palynivores.

In non-flowering seed plants, pollen germinates in the pollen chamber, located beneath the micropyle, underneath the integuments of the ovule. A pollen tube is produced, which grows into the nucellus to provide nutrients for the developing sperm cells. Sperm cells of Pinophyta and Gnetophyta are without flagella, and are carried by the pollen tube, while those of Cycadophyta and Ginkgophyta have many flagella.

When placed on the stigma of a flowering plant, under favorable circumstances, a pollen grain puts forth a pollen tube, which grows down the tissue of the style to the ovary, and makes its way along the placenta, guided by projections or hairs, to the micropyle of an ovule. The nucleus of the tube cell has meanwhile passed into the tube, as does also the generative nucleus, which divides (if it has not already) to form two sperm cells. The sperm cells are carried to their destination in the tip of the pollen tube. Double-strand breaks in DNA that arise during pollen tube growth appear to be efficiently repaired in the generative cell that carries the male genomic information to be passed on to the next plant generation.{{cite journal |vauthors=Hirano T, Takagi K, Hoshino Y, Abe T |title=DNA damage response in male gametes of Cyrtanthus mackenii during pollen tube growth |journal=AoB Plants |volume=5 |pages=plt004 |year=2013 |pmid=23550213 |pmc=3583183 |doi=10.1093/aobpla/plt004}} However, the vegetative cell that is responsible for tube elongation appears to lack this DNA repair capability.

{{Main article|Palynology}}

The sporopollenin outer sheath of pollen grains affords them some resistance to the rigours of the fossilisation process that destroy weaker objects; it is also produced in huge quantities. There is an extensive fossil record of pollen grains, often disassociated from their parent plant. The discipline of palynology is devoted to the study of pollen, which can be used both for biostratigraphy and to gain information about the abundance and variety of plants alive — which can itself yield important information about paleoclimates. Also, pollen analysis has been widely used for reconstructing past changes in vegetation and their associated drivers.{{cite journal |last1=Franco-Gaviria |first1=Felipe |last2=Caballero-Rodríguez |first2=Dayenari |last3=Correa-Metrio |first3=Alexander |last4=Pérez |first4=Liseth |last5=Schwalb |first5=Antje |last6=Cohuo |first6=Sergio |last7=Macario-González |first7=Laura |title=The human impact imprint on modern pollen spectra of the Maya lands |journal=Boletín de la Sociedad Geológica Mexicana |date=6 April 2018 |volume=70 |issue=1 |pages=61–78 |doi=10.18268/bsgm2018v70n1a4|doi-access=free |bibcode=2018BSGMx..70...61F }}

Pollen is first found in the fossil record in the late Devonian period,{{Cite book| last = Traverse | first = Alfred | chapter = Chapter 8: Devonian Palynology | pages=199–227 | title = Paleopalynology | volume = 28 |series = Topics in Geobiology, 28 | year =2007 | publisher = Springer | location = Dordrecht | isbn = 978-1-4020-6684-9 | doi = 10.1007/978-1-4020-5610-9_8}}{{cite journal |last1=Wang |first1=De-Ming |last2=Meng |first2=Mei-Cen |last3=Guo |first3=Yun |title=Pollen Organ Telangiopsis sp. of Late Devonian Seed Plant and Associated Vegetative Frond |year=2016 |journal=PLOS ONE |volume=11 |issue=1 |pages=e0147984 |doi=10.1371/journal.pone.0147984 |pmid=26808271 |pmc=4725745 |bibcode=2016PLoSO..1147984W |doi-access=free}} but at that time it is indistinguishable from spores. It increases in abundance until the present day.

{{see also|Allergy season}}

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{{More citations needed section|date = March 2013}}

{{expand section|information about allergies not in the nose, e.g., skin reactions|date=March 2013}}

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File:Pine releasing pollen into the wind in Tuntorp 4.jpg releasing pollen into the wind]]

Nasal allergy to pollen is called pollinosis, and allergy specifically to grass pollen is called hay fever. Generally, pollens that cause allergies are those of anemophilous plants (pollen is dispersed by air currents.) Such plants produce large quantities of lightweight pollen (because wind dispersal is random and the likelihood of one pollen grain landing on another flower is small), which can be carried for great distances and are easily inhaled, bringing it into contact with the sensitive nasal passages.

Pollen allergies are common in polar and temperate climate zones, where production of pollen is seasonal. In the tropics pollen production varies less by the season, and allergic reactions less.

In northern Europe, common pollens for allergies are those of birch and alder, and in late summer wormwood and different forms of hay. Grass pollen is also associated with asthma exacerbations in some people, a phenomenon termed thunderstorm asthma.{{cite journal |last1=Erbas |first1=B. |last2=Jazayeri |first2=M. |last3=Lambert |first3=K. A. |last4=Katelaris |first4=C. H. |last5=Prendergast |first5=L. A. |last6=Tham |first6=R. |last7=Parrodi |first7=M. J. |last8=Davies |first8=J. |last9=Newbigin |first9=E. |last10=Abramson |first10=M. J. |last11=Dharmage |first11=S. C. |title=Outdoor pollen is a trigger of child and adolescent asthma emergency department presentations: A systematic review and meta-analysis |journal=Allergy |date=August 2018 |volume=73 |issue=8 |pages=1632–1641 |doi=10.1111/all.13407 |pmid=29331087 |doi-access=free|hdl=11343/283486 |hdl-access=free }}

In the US, people often mistakenly blame the conspicuous goldenrod flower for allergies. Since this plant is entomophilous (its pollen is dispersed by animals), its heavy, sticky pollen does not become independently airborne. Most late summer and fall pollen allergies are probably caused by ragweed, a widespread anemophilous plant.{{cite web|last1=Oder|first1=Tom|title=Dear allergy sufferers: Don't blame goldenrod|url=http://www.mnn.com/health/allergies/stories/dear-allergy-sufferers-dont-blame-goldenrod|website=mnn.com|publisher=Mother Nature Network|access-date=18 July 2016}}

Arizona was once regarded as a haven for people with pollen allergies, although several ragweed species grow in the desert. However, as suburbs grew and people began establishing irrigated lawns and gardens, more irritating species of ragweed gained a foothold and Arizona lost its claim of freedom from hay fever.

Anemophilous spring blooming plants such as oak, birch, hickory, pecan, and early summer grasses may also induce pollen allergies. Most cultivated plants with showy flowers are entomophilous and do not cause pollen allergies.

Symptoms of pollen allergy include sneezing, itchy, or runny nose, nasal congestion, red, itchy, and watery eyes. Substances, including pollen, that cause allergies can trigger asthma. A study found a 54% increased chance of asthma attacks when exposed to pollen.{{Cite journal|date=2015-09-01|title=Allergy and asthma: Effects of the exposure to particulate matter and biological allergens|journal=Respiratory Medicine|language=en|volume=109|issue=9|pages=1089–1104|doi=10.1016/j.rmed.2015.05.017|issn=0954-6111|last1=Baldacci|first1=S.|last2=Maio|first2=S.|last3=Cerrai|first3=S.|last4=Sarno|first4=G.|last5=Baïz|first5=N.|last6=Simoni|first6=M.|last7=Annesi-Maesano|first7=I.|last8=Viegi|first8=G.|author9=HEALS Study|pmid=26073963|s2cid=205000320|doi-access=free}}

The number of people in the United States affected by hay fever is between 20 and 40 million, including around 6.1 million children{{Cite web|title=Allergy Facts {{!}} AAFA.org|url=http://www.aafa.org/allergy-facts|access-date=2021-07-12|website=www.aafa.org|language=en}}{{cite journal |last1=Skoner |first1=David P. |title=Allergic rhinitis: Definition, epidemiology, pathophysiology, detection, and diagnosis |journal=Journal of Allergy and Clinical Immunology |date=July 2001 |volume=108 |issue=1 |pages=S2–S8 |doi=10.1067/mai.2001.115569 |pmid=11449200|doi-access=free }} and such allergy has proven to be the most frequent allergic response in the nation. Hay fever affects about 20% of Canadians and the prevalence is increasing.{{cite journal|last1=Sierra-Heredia|first1=Cecilia|last2=North|first2=Michelle|last3=Brook|first3=Jeff|last4=Daly|first4=Christina|last5=Ellis|first5=Anne K.|last6=Henderson|first6=Dave|last7=Henderson|first7=Sarah B.|author-link7=Sarah B. Henderson|last8=Lavigne|first8=Éric|last9=Takaro|first9=Tim K.|date=August 2018|title=Aeroallergens in Canada: Distribution, Public Health Impacts, and Opportunities for Prevention|journal=International Journal of Environmental Research and Public Health|volume=15|issue=8|page=1577|doi=10.3390/ijerph15081577|pmc=6121311|pmid=30044421|doi-access=free}} There are certain evidential suggestions pointing out hay fever and similar allergies to be of hereditary origin. Individuals who suffer from eczema or are asthmatic tend to be more susceptible to developing long-term hay fever.[http://www.webmd.com/allergies/living-with-allergies-10/rhinitis Allergies and Hay Fever] WebMD. Retrieved on 2010-03-09

Since 1990, pollen seasons have gotten longer and more pollen-filled, and climate change is responsible, according to a new study.{{Cite journal|last1=Anderegg|first1=William R. L.|last2=Abatzoglou|first2=John T.|last3=Anderegg|first3=Leander D. L.|last4=Bielory|first4=Leonard|last5=Kinney|first5=Patrick L.|last6=Ziska|first6=Lewis|date=2021-02-16|title=Anthropogenic climate change is worsening North American pollen seasons|journal=Proceedings of the National Academy of Sciences|language=en|volume=118|issue=7|pages=e2013284118|doi=10.1073/pnas.2013284118|issn=0027-8424|pmid=33558232|pmc=7896283|bibcode=2021PNAS..11813284A|doi-access=free }} The researchers attributed roughly half of the lengthening pollen seasons and 8% of the trend in pollen concentrations to climate changes driven by human activity.{{Cite web|last1=Boston|first1=677 Huntington Avenue|last2=Ma 02115 +1495‑1000|date=2021-02-18|title=Pollen seasons are getting longer, driven by climate change|url=https://www.hsph.harvard.edu/news/hsph-in-the-news/pollen-seasons-are-getting-longer-driven-by-climate-change/|access-date=2021-07-12|website=News|language=en-us}}

In Denmark, decades of rising temperatures cause pollen to appear earlier and in greater amounts, exacerbated by the introduction of new species such as ragweed.Siewertsen, Bjarne. "[http://www.dmi.dk/nyheder/arkiv/nyheder-2015/04/haard-nyser-for-allergikere-i-varm-fremtid/ Hård nyser for allergikere i varm fremtid] {{Webarchive|url=https://web.archive.org/web/20150419165510/http://www.dmi.dk/nyheder/arkiv/nyheder-2015/04/haard-nyser-for-allergikere-i-varm-fremtid/ |date=2015-04-19}}" (English: Hard sneeze for allergic people in warm future) Danish Meteorological Institute, 18 April 2015. Retrieved: 19 April 2015.

The most efficient way to handle a pollen allergy is by preventing contact with the material. Individuals carrying the ailment may at first believe that they have a simple summer cold, but hay fever becomes more evident when the apparent cold does not disappear. The confirmation of hay fever can be obtained after examination by a general physician.[http://www.allergiesandtreatments.com/pollen-allergy/ Bee, grass pollen allergy symptoms] {{Webarchive|url=https://web.archive.org/web/20091010200012/http://www.allergiesandtreatments.com/pollen-allergy/ |date=2009-10-10}}. allergiesandtreatments.com. Retrieved on 2010-03-09

{{main article|Allergic rhinitis#treatment}}

Antihistamines are effective at treating mild cases of pollinosis; this type of non-prescribed drugs includes loratadine, cetirizine and chlorpheniramine. They do not prevent the discharge of histamine, but it has been proven that they do prevent a part of the chain reaction activated by this biogenic amine, which considerably lowers hay fever symptoms.

Decongestants can be administered in different ways such as tablets and nasal sprays.

Allergy immunotherapy (AIT) treatment involves administering doses of allergens to accustom the body to pollen, thereby inducing specific long-term tolerance.{{cite journal |last1=Moingeon |first1=P. |last2=Batard |first2=T. |last3=Fadel |first3=R. |last4=Frati |first4=F. |last5=Sieber |first5=J. |last6=Overtvelt |first6=L. |title=Immune mechanisms of allergen-specific sublingual immunotherapy. |journal=Allergy |date=February 2006 |volume=61 |issue=2 |pages=151–165 |doi=10.1111/j.1398-9995.2006.01002.x |pmid=16409190 |s2cid=36043612}} Allergy immunotherapy can be administered orally (as sublingual tablets or sublingual drops), or by injections under the skin (subcutaneous). Discovered by Leonard Noon and John Freeman in 1911, allergy immunotherapy represents the only causative treatment for respiratory allergies.

Most major classes of predatory and parasitic arthropods contain species that eat pollen, despite the common perception that bees are the primary pollen-consuming arthropod group. Many Hymenoptera other than bees consume pollen as adults, though only a small number feed on pollen as larvae (including some ant larvae). Spiders are normally considered carnivores but pollen is an important source of food for several species, particularly for spiderlings, which catch pollen on their webs.{{Cite journal |last1=Eggs |first1=Benjamin |last2=Sanders |first2=Dirk |date=2013-11-29 |title=Herbivory in Spiders: The Importance of Pollen for Orb-Weavers |journal=PLOS ONE |language=en |volume=8 |issue=11 |pages=e82637 |doi=10.1371/journal.pone.0082637 |doi-access=free |issn=1932-6203 |pmc=3843719 |pmid=24312430|bibcode=2013PLoSO...882637E }} Some predatory mites also feed on pollen, with some species being able to subsist solely on pollen, such as Euseius tularensis, which feeds on the pollen of dozens of plant species. Members of some beetle families such as Mordellidae and Melyridae feed almost exclusively on pollen as adults, while various lineages within larger families such as Curculionidae, Chrysomelidae, Cerambycidae, and Scarabaeidae are pollen specialists even though most members of their families are not (e.g., only 36 of 40,000 species of ground beetles, which are typically predatory, have been shown to eat pollen—but this is thought to be a severe underestimate as the feeding habits are only known for 1,000 species). Similarly, Ladybird beetles mainly eat insects, but many species also eat pollen, as either part or all of their diet. Hemiptera are mostly herbivores or omnivores but pollen feeding is known (and has only been well studied in the Anthocoridae). Many adult flies, especially Syrphidae, feed on pollen, and three UK syrphid species feed strictly on pollen (syrphids, like all flies, cannot eat pollen directly due to the structure of their mouthparts, but can consume pollen contents that are dissolved in a fluid).{{Cite book| chapter=The Pollen Feeders| title=Relationships of Natural Enemies and Non-Prey Foods| volume=7| pages=87–116| year=2009| isbn=978-1-4020-9234-3| doi=10.1007/978-1-4020-9235-0_6| last1=Lundgren| first1=Jonathan G.}} Some species of fungus, including Fomes fomentarius, are able to break down grains of pollen as a secondary nutrition source that is particularly high in nitrogen.{{cite book |title= Fungal Strategies of Wood Decay in Trees|author1=Schwarze, Francis W. M. R. |author2=Engels, Julia |author3=Mattheck, Claus |name-list-style=amp |year= 2000|publisher= Springer|isbn= 978-3-540-67205-0|page= 61}} Pollen may be valuable diet supplement for detritivores, providing them with nutrients needed for growth, development and maturation.{{cite journal |last1=Filipiak |first1=Michał |title=Pollen Stoichiometry May Influence Detrital Terrestrial and Aquatic Food Webs |journal=Frontiers in Ecology and Evolution |date=15 December 2016 |volume=4 |doi=10.3389/fevo.2016.00138 |doi-access=free}} It was suggested that obtaining nutrients from pollen, deposited on the forest floor during periods of pollen rains, allows fungi to decompose nutritionally scarce litter.

Some species of Heliconius butterflies consume pollen as adults, which appears to be a valuable nutrient source, and these species are more distasteful to predators than the non-pollen consuming species.{{cite journal |last1=Salcedo |first1=C. |title=Evidence of pollen digestion at nocturnal aggregations of Heliconius sara in Costa Rica (Lepidoptera: Nymphalidae) |journal=Tropical Lepidoptera Research |date=1 June 2010 |pages=35–37 |url=https://journals.flvc.org/troplep/article/view/90278}}{{cite journal |vauthors=Cardoso MZ, Gilbert LE |title=Pollen feeding, resource allocation and the evolution of chemical defence in passion vine butterflies |journal=Journal of Evolutionary Biology |volume=26 |issue=6 |pages=1254–60 |date=June 2013 |pmid=23662837 |doi=10.1111/jeb.12119 |s2cid=206046558 |doi-access=free}}

Although bats, butterflies, and hummingbirds are not pollen eaters per se, their consumption of nectar in flowers is an important aspect of the pollination process.

Bee pollen for human consumption is marketed as a food ingredient and as a dietary supplement. The largest constituent is carbohydrates, with protein content ranging from 7 to 35 percent depending on the plant species collected by bees.Sanford, Malcolm T. {{cite web |url=http://edis.ifas.ufl.edu/AA158 |title=Producing Pollen |date=17 May 2006 |access-date=2015-07-15 |archive-url=https://web.archive.org/web/20070113100544/http://edis.ifas.ufl.edu/AA158 |archive-date=January 13, 2007}}, University of Florida, Institute of Food and Agricultural Sciences; citing P. Witherell, "Other Products of the Hive," Chapter XVIII, The Hive and the Honey Bee, Dadant & Sons, Inc., Hamilton, IL, 1975.

Honey produced by bees from natural sources contains pollen derived p-coumaric acid,{{cite journal |vauthors=Mao W, Schuler MA, Berenbaum MR |title=Honey constituents up-regulate detoxification and immunity genes in the western honey bee Apis mellifera |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=110 |issue=22 |pages=8842–6 |date=May 2013 |pmid=23630255 |pmc=3670375 |doi=10.1073/pnas.1303884110 |bibcode=2013PNAS..110.8842M |doi-access=free}} an antioxidant and natural bactericide that is also present in a wide variety of plants and plant-derived food products.{{cite journal |first1=Zaixiang |last1=Lou|first2=Hongxin |last2=Wang |first3=Shengqi |last3=Rao |first4=Juntao |last4=Sun |first5=Chaoyang |last5=Ma |first6=Jing |last6=Li |journal=Food Control|volume=25 |issue=2 |date=2012|pages=550–554 |title=p-Coumaric acid kills bacteria through dual damage mechanisms |doi=10.1016/j.foodcont.2011.11.022}}

The U.S. Food and Drug Administration (FDA) has not found any harmful effects of bee pollen consumption, except for the usual allergies. However, FDA does not allow bee pollen marketers in the United States to make health claims about their produce, as no scientific basis for these has ever been proven. Furthermore, there are possible dangers not only from allergic reactions but also from contaminants such as pesticides and from fungi and bacteria growth related to poor storage procedures. A manufacturers's claim that pollen collecting helps the bee colonies is also controversial.{{cite web| url=http://edis.ifas.ufl.edu/AA158 |access-date=2007-08-30 |title=Producing Pollen |last=Sanford |first=Malcolm T. |publisher=University of Florida, Institute of Food and Agricultural Sciences |archive-url=https://web.archive.org/web/20010429230017/http://edis.ifas.ufl.edu/AA158 |archive-date=2001-04-29}} Document ENY118. Original publication date November 1, 1994. Revised February 1, 1995. Reviewed May 1, 2003.

Pine pollen ({{Korean|hangul=송화가루|rr=Songhwa Garu|labels=no}}) is traditionally consumed in Korea as an ingredient in sweets and beverages.{{Cite news|url=https://aarongilbreath.wordpress.com/2013/05/31/ginseng-pine-pollen-and-honey-five-korean-teas-and-where-to-drink-them-in-seoul/|title=Source|newspaper=Aarongilbreath's Blog|date=2013-05-31}} Māori of precolonial New Zealand would gather pollen of Typha orientalis to make a special bread called pungapunga.{{cite journal |last1=Neill |first1=Lindsay |last2=Sturny |first2=Arno |title=Pāraoa Rēwena: The Relegation of Aotearoa New Zealand's Indigenous Bread |journal=Sites: A Journal of Social Anthropology and Cultural Studies |date=Aug 2022 |volume=19 |issue=1 |page=65 |doi=10.11157/sites-id505}}

The growing industries in pollen harvesting for human and bee consumption rely on harvesting pollen baskets from honey bees as they return to their hives using a pollen trap.{{cite web | url=https://www.youtube.com/watch?v=JBP9pw2rNk4 | archive-url=https://ghostarchive.org/varchive/youtube/20211104/JBP9pw2rNk4| archive-date=2021-11-04 | url-status=live| title=How a Pollen Trap Works (Bee Pollen)| website=YouTube| date=30 April 2014}}{{cbignore}} When this pollen has been tested for parasites, it has been found that a multitude of viruses and eukaryotic parasites are present in the pollen.{{cite journal |last1=Graystock |first1=Peter |last2=Yates |first2=Kathryn |last3=Evison |first3=Sophie E. F. |last4=Darvill |first4=Ben |last5=Goulson |first5=Dave |last6=Hughes |first6=William O. H. |s2cid=3937352 |title=The Trojan hives: pollinator pathogens, imported and distributed in bumblebee colonies |journal=Journal of Applied Ecology |date=July 2013 |volume=50 |issue=5 |pages=1207–1215 |doi=10.1111/1365-2664.12134|bibcode=2013JApEc..50.1207G }}{{cite journal |last1=Singh |first1=Rajwinder |last2=Levitt |first2=Abby L. |last3=Rajotte |first3=Edwin G. |last4=Holmes |first4=Edward C. |last5=Ostiguy |first5=Nancy |last6=vanEngelsdorp |first6=Dennis |last7=Lipkin |first7=W. Ian |last8=dePamphilis |first8=Claude W. |last9=Toth |first9=Amy L. |last10=Cox-Foster |first10=Diana L. |last11=Traveset |first11=Anna |title=RNA Viruses in Hymenopteran Pollinators: Evidence of Inter-Taxa Virus Transmission via Pollen and Potential Impact on Non-Apis Hymenopteran Species |journal=PLOS ONE |date=22 December 2010 |volume=5 |issue=12 |pages=e14357 |doi=10.1371/journal.pone.0014357 |pmid=21203504 |pmc=3008715|bibcode=2010PLoSO...514357S|doi-access=free}} It is currently unclear if the parasites are introduced by the bee that collected the pollen or if it is from the flower.{{cite journal |last1=Graystock |first1=Peter |last2=Goulson |first2=Dave |last3=Hughes |first3=William O. H. |title=Parasites in bloom: flowers aid dispersal and transmission of pollinator parasites within and between bee species |journal=Proceedings of the Royal Society B: Biological Sciences |date=5 August 2015 |volume=282 |issue=1813 |pages=20151371 |doi=10.1098/rspb.2015.1371 |pmid=26246556 |pmc=4632632}} Though this is not likely to pose a risk to humans, it is a major issue for the bumblebee rearing industry that relies on thousands of tonnes of honey bee collected pollen per year.{{cite journal |last1=Graystock |first1=Peter |last2=Blane |first2=Edward J. |last3=McFrederick |first3=Quinn S. |last4=Goulson |first4=Dave |last5=Hughes |first5=William O.H. |title=Do managed bees drive parasite spread and emergence in wild bees? |journal=International Journal for Parasitology: Parasites and Wildlife |volume=5 |issue=1 |pages=64–75 |date=October 2015 |doi=10.1016/j.ijppaw.2015.10.001 |pmid=28560161 |pmc=5439461}} Several sterilization methods have been employed, though no method has been 100% effective at sterilisation without reducing the nutritional value of the pollen {{cite journal |last1=Graystock |first1=P. |last2=Jones |first2=J.C. |last3=Pamminger |first3=T. |last4=Parkinson |first4=J.F. |last5=Norman |first5=V. |last6=Blane |first6=E.J. |last7=Rothstein |first7=L. |last8=Wäckers |first8=F.|last9=Goulson |first9=D. |last10=Hughes |first10=W.O.H. |title=Hygienic food to reduce pathogen risk to bumblebees |journal=Journal of Invertebrate Pathology |date=May 2016 |volume=136 |pages=68–73 |doi=10.1016/j.jip.2016.03.007 |pmid=26970260|bibcode=2016JInvP.136...68G }}

{{Main article|Forensic palynology}}

File:RedbudPollen.TIF of redbud pollen. Scanning electron microscopes are major instruments in palynology.]]

In forensic biology, pollen can tell a lot about where a person or object has been, because regions of the world, or even more particular locations such a certain set of bushes, will have a distinctive collection of pollen species.{{cite web| title=Forensic Palynology: A New Way to Catch Crooks |author=Bryant, Vaughn M. |url=http://www.crimeandclues.com/pollen.htm |work=crimeandclues.com |archive-url= https://web.archive.org/web/20070203104441/http://www.crimeandclues.com/pollen.htm |archive-date=2007-02-03}} Pollen evidence can also reveal the season in which a particular object picked up the pollen.{{Cite news| title=Forensics studies look to pollen |author=Stackhouse, Robert |date=17 April 2003 |url=http://www.thebatt.com/2.8526/forensics-studies-look-to-pollen-1.1224833#.UXXYzlfHn-E |archive-url=https://web.archive.org/web/20130423004144/http://www.thebatt.com/2.8526/forensics-studies-look-to-pollen-1.1224833 |archive-date=2013-04-23 |newspaper=The Battalion}} Pollen has been used to trace activity at mass graves from the Bosnian War,{{cite news| url=http://news.bbc.co.uk/1/hi/sci/tech/3640788.stm |title=Pollen helps war crime forensics |author=Wood, Peter| date=9 September 2004 |work=BBC News}} catch a burglar who brushed against a Hypericum bush during a crime,{{Cite journal| doi=10.1016/j.forsciint.2005.11.028 |title=Hypericum pollen determines the presence of burglars at the scene of a crime: An example of forensic palynology |journal=Forensic Science International |volume=163 |issue=3 |pages=231–235 |author=D. Mildenhall |pmid=16406430 |year=2006}} and has even been proposed as an additive for bullets to enable tracking them.{{cite journal |title=Newscripts |journal= Chemical & Engineering News |volume=86 |issue=33 |date=18 August 2008 |page=88 |author=Wolf, Lauren K. |url=http://cen.acs.org/articles/86/i33/Newscripts.html |doi=10.1021/cen-v086n033.p088}}

In some Native American religions, pollen was used in prayers and rituals to symbolize life and renewal by sanctifying objects, dancing grounds, trails, and sandpaintings. It may also be sprinkled over heads or in mouths. Many Navajo people believed the body became holy when it traveled over a trail sprinkled with pollen.{{Cite book|title=Encyclopedia of Native American Religions|last=Hirshfelder|first=Arlene|publisher=Facts on File, Inc.|year=2000|isbn=978-0816039494|pages=225}}

For agricultural research purposes, assessing the viability of pollen grains can be necessary and illuminating. A very common, efficient method to do so is known as Alexander's stain. This differential stain consists of ethanol, malachite green, distilled water, glycerol, phenol, chloral hydrate, acid fuchsin, orange G, and glacial acetic acid.{{cite journal |last1=Alexander |first1=M. P. |title=Differential Staining of Aborted and Nonaborted Pollen |journal=Stain Technology |date=1 January 1969 |volume=44 |issue=3 |pages=117–122 |doi=10.3109/10520296909063335 |pmid=4181665}} (A less-toxic variation omits the phenol and chloral hydrate{{cite journal | last1 = Peterson | first1 = Ross | last2 = Slovin | first2 = Janet P. | last3 = Chen | first3 = Changbin | title = A Simplified Method for Differential Staining of Aborted and Non-Aborted Pollen Grains | journal = International Journal of Plant Biology | date = 23 July 2010 | volume = 1 | issue = 2 | page = e13 | eissn = 2037-0164 | doi = 10.4081/pb.2010.e13 | pmid = | url = | doi-access = free }}.) In angiosperms and gymnosperms non-aborted pollen grain will appear red or pink, and aborted pollen grains will appear blue or slightly green.

• European Pollen Database
• Evolution of sex
• Honeybee starvation
• Pollen calendar
• Pollen count
• Pollen DNA barcoding
• Pollen source
• Polyphenol antioxidant
• Bee pollen

{{reflist}}

{{refbegin|30em}}

• {{cite book|last=Simpson|first=Michael G.|title=Plant Systematics|year=2011|publisher=Academic Press|isbn=978-0-08-051404-8|url=https://books.google.com/books?id=Ia2eIPVksMMC|access-date=12 February 2014}}
• {{cite book|last=Singh|first=Gurcharan|title=Plant Systematics: An Integrated Approach|year=2004|publisher=Science Publishers|isbn=978-1-57808-351-0|url=https://books.google.com/books?id=In_Lv8iMt24C|access-date=23 January 2014}}
• {{cite journal |last1=Furness |first1=Carol A. |last2=Rudall |first2=Paula J. |author-link2=Paula Rudall|title=Inaperturate Pollen in Monocotyledons |journal=International Journal of Plant Sciences |date=1999 |volume=160 |issue=2 |pages=395–414 |doi=10.1086/314129 |jstor=314129 |bibcode=1999IJPlS.160..395F |s2cid=83903452}}
• {{cite web |title=Pollen Grain Surface Pattern Terminology |url=https://research.fit.edu/media/site-specific/researchfitedu/applied-biogeography/documents/protocols/Quick-Reference-Glossary-with-Illustrations.pdf |archive-url=https://web.archive.org/web/20190811164518/https://research.fit.edu/media/site-specific/researchfitedu/applied-biogeography/documents/protocols/Quick-Reference-Glossary-with-Illustrations.pdf |archive-date=2019-08-11 |url-status=live |website=Quick Reference Glossary with Illustrations |publisher=Florida Institute of Technology: Center for Applied Biogeography |access-date=11 August 2019 |date=October 2014}}
• {{cite web |last1=Society for the Promotion of Palynological Research in Austria |title=Illustrated Pollen Terms |url=https://www.paldat.org/terminology/tools |website=PalDat - Palynological Database |publisher=University of Vienna. Division of Structural and Functional Botany |access-date=16 January 2021 |date=2021}}
• {{cite web|last=Davis|first=Owen|url=http://www.geo.arizona.edu/palynology/polkey.html#keyauthor=Owen|title=Palynology — Pollen|publisher=University of Arizona. Department of Geosciences|date=1999|access-date=2009-02-19|archive-url=https://web.archive.org/web/20051222142511/http://www.geo.arizona.edu/palynology/polkey.html#keyauthor=Owen|archive-date=2005-12-22}}
• {{cite web |last1=Kaltenrieder |first1=Petra |last2=von Ballmoos |first2=Peter |title=Types of Apertures in microspores |url=http://www.botany.unibe.ch/paleo/pollen_e/apertures.htm |website=Introduction to pollen analysis |publisher=Institute of Plant Sciences, University of Bern |access-date=28 June 2021 |date=2003}}

{{refend}}

{{Commons category}}

{{Scholia|topic}}

• [https://web.archive.org/web/20050527035527/http://www.geo.arizona.edu/palynology/polident.html Pollen and Spore Identification Literature]
• [https://web.archive.org/web/20110811072853/http://albertlleal.com/en/reports/category/10-pollen-micrographs.html Pollen micrographs at SEM and confocal microscope]
• [https://web.archive.org/web/20110721173444/http://www.gmo-safety.eu/science-live/128.maize-outcrossing-flight-pollen-cloud.html The flight of a pollen cloud]
• [http://www.paldat.org/ PalDat (database comprising palynological data from a variety of plant families)]
• [https://pollen.tstebler.ch/MediaWiki/ Pollen-Wiki - A digital Pollen-Atlas], retrieved 9 February 2018.
• [https://www.youtube.com/watch?v=xZcrktbNjcc YouTube video of pollen clouds from Juncus gerardii plants]

{{Botany}}

{{Authority control}}

Category:Plant anatomy

Category:Plant morphology

Category:Pollination

Category:Allergology