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Pollen is a powdery substance consisting of pollen grains which are microsporophytes of
seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to E ...

seed plants
, which produce male
gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply ...
s (sperm cells). Pollen grains have a hard coat made of
sporopollenin 270px, Scanning electron microscope, SEM image of pollen grains Sporopollenin is one of the most chemically inert biological polymers. It is a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically ve ...
that protects the gametophytes during the process of their movement from the
stamen The stamen (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ve ...
s to the
pistil '' stigmas and style Gynoecium (, from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided in ...

pistil
of flowering plants, or from the male
cone A cone is a three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Greek language, Ancient Greek wikt:πα ...
to the female cone of
coniferous plants
coniferous plants
. If pollen lands on a compatible pistil or female cone, it
germinate seedlings, three days after germination Germination is the process by which an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell t ...
s, producing a
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
that transfers the
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
to the
ovule In seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or l ...

ovule
containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called
palynology pollen File:Pollen Tube.svg, Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard ...
and is highly useful in
paleoecology Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescale The geologic time scale (GTS) is a system of chronological datingCh ...
,
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes th ...
,
archaeology Archaeology or archeology is the study of human activity through the recovery and analysis Analysis is the process of breaking a complexity, complex topic or Substance theory, substance into smaller parts in order to gain a better underst ...
, and
forensics Forensic science, also known as criminalistics, is the application of to and , mainly—on the criminal side—during , as governed by the legal standards of and . Forensic scientists collect, preserve, and analyze scientific during the c ...
. Pollen in plants is used for transferring haploid male genetic material from the
anther The stamen (plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greate ...
of a single flower to the
stigma Stigma or plural stigmata, stigmas may refer to: * Social stigma, the disapproval of a person based on physical or behavioral characteristics that distinguish them from others Symbolism * Stigmata, bodily marks or wounds resembling the crucifix ...
of another in cross-pollination. In a case of self-pollination, this process takes place from the anther of a flower to the stigma of the same flower. Pollen is infrequently used as food and
food supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder or liquid. A supplement can provide nutrient A nutrient is a substance used by an organism to survive, grow, and ...
. Because of agricultural practices, it is often contaminated by agricultural pesticides.


Structure and formation

Pollen itself is not the male gamete. Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell. In flowering plants the vegetative tube cell produces the
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
, and the generative cell divides to form the two sperm nuclei. File:Oenothera speciosa pollen 200x.jpg, Triporate pollen of ''
Oenothera speciosa ''Oenothera speciosa'' is a species of evening primrose known by several common names, including pinkladies, pink evening primrose, showy evening primrose, Mexican primrose, amapola, and buttercups (not to be confused with true buttercups in the g ...

Oenothera speciosa
'' File:Lilium auratum - pollen.jpg, Pollen of ''
Lilium auratum ''Lilium auratum'' ( ja, 山百合, yamayuri, label=none, literally "mountain lily") is one of the true lilies. It is native to Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red ci ...

Lilium auratum
'' showing single sulcus (monosulcate) File:Arabis voch1-4.jpg, ''
Arabis ''Arabis'' ,''Sunset Western Garden Book,'' 1995:606–607 or rockcress, is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms a ...

Arabis
'' pollen has three colpi and prominent surface structure. File:Жизнеспособность пыльцы 13.jpg, Apple pollen under microscopy


Formation

Pollen is produced in the
microsporangia Microsporangia are sporangia that produce microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have Heterospory, heterosporic life cycles, such as Spermatophyte, seed plants, Selagin ...
in the male cone of a conifer or other
gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also ...
or in the anthers of an
angiosperm Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ...

angiosperm
flower A flower, sometimes known as a bloom or blossom Image:Cerisier du Japon Prunus serrulata.jpg, Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plan ...

flower
. Pollen grains come in a wide variety of shapes, sizes, and surface markings characteristic of the species (see
electron micrograph A micrograph or photomicrograph is a photograph 396x396px, '' View from the Window at Le Gras'' (1826 or 1827), by Nicéphore Niépce, the earliest known surviving photograph of a real-world scene, made with a camera obscura A cam ...
, right). Pollen grains of
pine A pine is any conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The divi ...

pine
s,
fir Firs (''Abies'') are a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

fir
s, and
spruce A spruce is a tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including ...

spruce
s are winged. The smallest pollen grain, that of the
forget-me-not ''Myosotis'' ( ) is a genus of flowering plants in the family (biology), family Boraginaceae. The name comes from the Ancient Greek "mouse's ear", which the foliage is thought to resemble. In the northern hemisphere they are colloquially denomi ...

forget-me-not
(''Myosotis'' spp.), is 2.5-5  µm (0.005 mm) in diameter. Corn pollen grains are large, about 90–100 µm. Most grass pollen is around 20-25 µm. 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, four groups of sporogenous cells form within the anther. The fertile 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. In a process called microsporogenesis, four haploid
microspore Microspores are land plant The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encomp ...
s are produced from each diploid sporogenous cell (microsporocyte, pollen mother cell or meiocyte), after
meiotic division spermatocyte, played back at 120× the recorded speed Meiosis (; from Greek language, Greek μείωσις, ''meiosis'', meaning "lessening") is a special type of cell division of germ cells in Sexual reproduction, sexually-reproducing organism ...
. 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 Cytokinesis () is the part of the cell division biological process, process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of Mitosis, nuclear di ...

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 Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...

monocots
is successive, but there are important exceptions. During microgametogenesis, the unicellular microspores undergo mitosis and develop into mature microgametophytes containing the gametes. In some flowering plants,
germination seedlings, three days after germination Germination is the process by which an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell t ...

germination
of the pollen grain may begin even before it leaves the microsporangium, with the generative cell forming the two sperm cells.


Structure

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 Cellulose is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

cellulose
called the endospore or intine, and a tough resistant outer cuticularized wall composed largely of
sporopollenin 270px, Scanning electron microscope, SEM image of pollen grains Sporopollenin is one of the most chemically inert biological polymers. It is a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically ve ...
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, 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. They allow shrinking and swelling of the grain caused by changes in moisture content. The process of shrinking the grain is called harmomegathy. 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. 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. 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 A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
germination at any position. Terms such as uniaperturate and triaperturate refer to the number of apertures present (one and three respectively). 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. 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.
Eudicots The eudicots, Eudicotidae or eudicotyledons are a clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage ...
have pollen with three colpi (
tricolpate The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicots b ...
) or with shapes that are evolutionarily derived from tricolpate pollen. The evolutionary trend in plants has been from monosulcate to polycolpate or polyporate pollen. Additionally,
gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also ...
pollen grains often have air bladders, or vesicles, called sacci. The sacci are not actually balloons, but are sponge-like, and increase the
buoyancy Buoyancy (), or upthrust, is an upward exerted by a that opposes the of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bo ...

buoyancy
of the pollen grain and help keep it aloft in the wind, as most gymnosperms are
anemophilous Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including Poaceae, grasses, Cyperaceae, sedges, and Juncaceae, rushes. ...
. Pollen can be monosaccate, (containing one saccus) or bisaccate (containing two sacci). Modern
pine A pine is any conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The divi ...

pine
,
spruce A spruce is a tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including ...

spruce
, and yellowwood trees all produce saccate pollen.


Pollination

The transfer of pollen grains to the female reproductive structure (''
pistil '' stigmas and style Gynoecium (, from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided in ...
'' in angiosperms) is called
pollination Pollination is the transfer of pollen Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat ...

pollination
. This transfer can be mediated by the wind, in which case the plant is described as
anemophilous Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including Poaceae, grasses, Cyperaceae, sedges, and Juncaceae, rushes. ...
(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 covered with pollen Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertising in biology, adve ...
(literally insect-loving) plants produce pollen that is relatively heavy, sticky and
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
-rich, for dispersal by
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
pollinator A pollinator is an animal that moves pollen File:Pollen Tube.svg, Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes ...

pollinator
s attracted to their flowers. Many insects and some
mite Mites are small arachnid Arachnida () is a Class (biology), class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes orders containing spiders (the largest order), scorpions, ticks, mites, op ...
s are specialized to feed on pollen, and are called
palynivore Image:Bee Collecting Pollen 2004-08-14.jpg, 250px, A honeybee collecting pollen from a flower In zoology, a palynivore /pəˈlɪnəvɔːɹ/, meaning "pollen eater" (from Greek language, Greek παλύνω palunō, "strew, sprinkle", and Latin, vor ...
s. In non-flowering seed plants, pollen germinates in the pollen chamber, located beneath the
micropyleMicropyle may refer to: * Micropyle (botany) a minute opening in the integument of an ovule of a seed plant. * Micropyle (zoology), a differentiated area of surface in an egg, through which a sperm enters {{Disambiguation ...

micropyle
, underneath the integuments of the ovule. A
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
is produced, which grows into the
nucellus In seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or l ...
to provide nutrients for the developing sperm cells. Sperm cells of
Pinophyta Conifers are a group of cone-bearing seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plants are predominantly photosynthetic eukaryotes of the Kin ...

Pinophyta
and
Gnetophyta Gnetophyta () is a division of plants, grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three Relict (biology), relict genera: ''Gnetum'' (Family (biology), family Gn ...
are without
flagella A flagellum (; ) is a hairlike appendage that protrudes from a wide range of microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and ...

flagella
, and are carried by the pollen tube, while those of
Cycad :''For the insect, see Cicada.'' Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious ...

Cycad
ophyta and
Ginkgophyta Ginkgoales is a gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the ...
have many flagella. When placed on the
stigma Stigma or plural stigmata, stigmas may refer to: * Social stigma, the disapproval of a person based on physical or behavioral characteristics that distinguish them from others Symbolism * Stigmata, bodily marks or wounds resembling the crucifix ...
of a flowering plant, under favorable circumstances, a pollen grain puts forth a
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
, which grows down the tissue of the style to the
ovary The ovary is an organ found in the female reproductive system The female reproductive system is made up of the internal and external sex organs that function in reproduction of new offspring. In humans, the female reproductive system is im ...
, and makes its way along the
placenta The placenta is a temporary fetal organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. ...

placenta
, guided by projections or hairs, to the micropyle of an
ovule In seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or l ...

ovule
. The nucleus of the tube cell has meanwhile passed into the tube, as does also the generative nucleus, which divides (if it hasn't already) to form two sperm cells. The sperm cells are carried to their destination in the tip of the
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
. Double-strand breaks in DNA that arise during
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
growth appear to be efficiently in the generative cell that carries the male to be passed on to the next plant generation. However, the vegetative cell that is responsible for tube elongation appears to lack this
DNA repair DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene mol ...

DNA repair
capability.


In the fossil record

Pollen's
sporopollenin 270px, Scanning electron microscope, SEM image of pollen grains Sporopollenin is one of the most chemically inert biological polymers. It is a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically ve ...
outer sheath affords it 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 Biostratigraphy is the branch of stratigraphy through Jurassic strata of the Colorado Plateau area of southeastern Utah demonstrate the principles of stratigraphy. Stratigraphy is a branch of geology concerned with the study of rock (geology), roc ...
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. Pollen is first found in the
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
record in the late
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
period, but at that time it is indistinguishable from spores. It increases in abundance until the present day.


Allergy to pollen

Nasal allergy to pollen is called pollinosis, and allergy specifically to grass pollen is called
hay fever Allergic rhinitis, also known as hay fever, is a type of inflammation in the nose which occurs when the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from An ...
. 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 A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...

birch
and
alder Alder is the common name of a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classific ...

alder
, and in late summer and different forms of
hay Hay is grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or ...

hay
. Grass pollen is also associated with in some people, a phenomenon termed thunderstorm asthma. In the US, people often mistakenly blame the conspicuous
goldenrod Goldenrod is a common name for many species of flowering plants in the sunflower family, Asteraceae, commonly in reference to the genus ''Solidago''. Several genera, such as ''Euthamia'', were formerly included in a broader concept of the genus ...

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 Ragweeds are flowering plants in the genus ''Ambrosia'' in the aster family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to m ...

ragweed
, a widespread anemophilous plant.
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak) is a U.S. state, state in the Southwestern United States, Southwestern region of the United States. It is also usually considered part of the Mountain States, Mountain states. It is th ...

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 , 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 An oak is a tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including on ...

oak
,
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...

birch
,
hickory Hickory is a common name for trees In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method ...

hickory
,
pecan The pecan (''Carya illinoinensis'') is a species of hickory native to the southern United States and northern Mexico in the region of the Mississippi River. The tree is cultivated for its seed in the southern United States, primarily in Georgia ...

pecan
, and early summer
grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...

grass
es 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 A sneeze, or sternutation, is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucous membrane, mucosa. A sneeze expels air forcibly from the mouth an ...
, itchy, or runny nose,
nasal congestion Nasal congestion is the blockage of nasal breathing usually due to membranes lining the nose becoming swollen from inflamed blood vessels. Background In about 85% of cases, nasal congestion leads to mouth breathing rather than nasal breathing ...
, red, itchy, and watery eyes. Substances, including pollen, that cause allergies can trigger asthma. A study found a 54% increased chance of
asthma Asthma is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. Sharpe, Inc., 2002 based in Greenwich, ...

asthma
attacks when exposed to pollen. The number of people in the United States affected by hay fever is between 20 and 40 million, including around 6.1 million children and such allergy has proven to be the most frequent
allergic response An allergic response is a hypersensitive immune reaction to a substance that normally is harmless or would not cause an immune response in everyone. An allergic response may cause harmful symptoms such as itching Itch (also known as pruritus ...
in the nation. Hay fever affects about 20% of Canadians and the prevalence is increasing. There are certain evidential suggestions pointing out hay fever and similar allergies to be of hereditary origin. Individuals who suffer from
eczema Dermatitis is of the , typically characterized by iness, and a . In cases of short duration, there may be small s, while in long-term cases the skin may become . The area of skin involved can vary from small to covering the entire body. Derma ...

eczema
or are
asthma Asthma is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. Sharpe, Inc., 2002 based in Greenwich, ...

asthma
tic tend to be more susceptible to developing long-term hay fever. Since 1990, pollen seasons have gotten longer and more pollen-filled, and climate change is responsible, according to a new study. 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. In
Denmark Denmark ( da, Danmark, ) is a Nordic country The Nordic countries, or the Nordics, are a geographical and cultural region In geography, regions are areas that are broadly divided by physical characteristics ( physical geography), hu ...

Denmark
, decades of rising temperatures cause pollen to appear earlier and in greater numbers, as well as introduction of new species such as ragweed. 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.


Treatment

Antihistamines Antihistamines are pharmaceutical drug, drugs which treat allergic rhinitis and other allergies. Typically people take antihistamines as an inexpensive, Generic drug, generic, over-the-counter drug that can provide relief from nasal congestion, ...
are effective at treating mild cases of pollinosis; this type of non-prescribed drugs includes
loratadine Loratadine, sold under the brand name Claritin among others, is a medication used to treat allergies Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensi ...

loratadine
,
cetirizine Cetirizine, sold under the brand name Zyrtec among others, is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis Dermatitis (also known as eczema) is inflammation of the skin Skin is the layer of u ...

cetirizine
and
chlorpheniramine Chlorphenamine (CP, CPM), also known as chlorpheniramine, is an antihistamine used to treat the symptoms of allergic conditions such as allergic rhinitis Allergic rhinitis, also known as hay fever, is a type of inflammation in the nose whic ...
. They do not prevent the discharge of
histamine Histamine is an organic nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior ...

histamine
, but it has been proven that they do prevent a part of the chain reaction activated by this
biogenic amine A biogenic amine is a biogenic substance with one or more amine In organic chemistry, amines (, ) are organic compound, compounds and functional groups that contain a base (chemistry), basic nitrogen atom with a lone pair. Amines are formally ...
, which considerably lowers hay fever symptoms. Decongestants can be administered in different ways such as tablets and
nasal spray Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion Nasal congestion is the blockage of nasal breathing usually due to membranes lining the ...

nasal spray
s. Allergy immunotherapy (AIT) treatment involves administering doses of allergens to accustom the body to pollen, thereby inducing specific long-term tolerance. 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.


Nutrition

Most major classes of
predatory Predation is a biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical envi ...
and
parasitic Parasitism is a Symbiosis, symbiotic biological interactions, relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), ad ...
arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference showing that Euarthropoda is a phylum: ...
s contain species that eat pollen, despite the common perception that
bee Bees are flying insects closely related to wasps and ants, known for their role in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

bee
s are the primary pollen-consuming arthropod group. Many
Hymenoptera Hymenoptera is a large order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or wa ...

Hymenoptera
other than bees consume pollen as adults, though only a small number feed on pollen as
larva A larva (plural larvae ) is a distinct juvenile form many animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that f ...
e (including some
ant Ants are eusocial Eusociality (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population i ...

ant
larvae).
Spider Spiders (order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the ...

Spider
s are normally considered
carnivore A carnivore , meaning "meat Meat is animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume orga ...
s but pollen is an important source of food for several species, particularly for
spider Spiders (order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the ...

spider
lings, which catch pollen on their . It is not clear how spiderlings manage to eat pollen however, since their mouths are not large enough to consume pollen grains. Some 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 Carabidae, 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 Fly, flies, cannot eat pollen directly due to the structure of their mouthparts, but can consume pollen contents that are dissolved in a fluid). 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. Pollen may be valuable diet supplement for detritivores, providing them with nutrients needed for growth, development and maturation. 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. Although bats, butterfly, butterflies and hummingbirds are not pollen eaters ''Per se (terminology), per se'', their consumption of nectar in flowers is an important aspect of the
pollination Pollination is the transfer of pollen Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat ...

pollination
process.


In humans

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. Honey produced by bees from natural sources contains pollen derived p-coumaric acid, an antioxidant and natural bactericide that is also present in a wide variety of plants and plant-derived food products. The U.S. Food and Drug Administration (FDA) has not found any harmful effects of bee pollen consumption, except from 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. Pine pollen () is traditionally consumed in Korea as an ingredient in sweets and beverages.


Parasites

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''. 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. It is currently unclear if the parasites are introduced by the bee that collected the pollen or if it is from the flower. 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. Several sterilization methods have been employed, though no method has been 100% effective at sterilisation without reducing the nutritional value of the pollen


Forensic 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. Pollen evidence can also reveal the season in which a particular object picked up the pollen. Pollen has been used to trace activity at mass graves in Bosnia, catch a burglar who brushed against a ''Hypericum'' bush during a crime, and has even been proposed as an additive for bullets to enable tracking them.


Spiritual purposes

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.


Pollen grain staining

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. In angiosperms and gymnosperms non-aborted pollen grain will appear red or pink, and aborted pollen grains will appear blue or slightly green.


See also

* European Pollen Database * Evolution of sex * Honeybee starvation * Pollen calendar * Pollen count * Pollen DNA barcoding * Pollen source * Polyphenol antioxidant


References


Bibliography

* * * * * *


External links


Pollen and Spore Identification Literature





PalDat (database comprising palynological data from a variety of plant families)

''Pollen-Wiki - A digital Pollen-Atlas''
abgerufen am 09. Februar 2018.
YouTube video of pollen clouds from Juncus gerardii plants
{{Authority control Plant anatomy Plant morphology Palynology, Pollination Allergology