Pollen

Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction.

Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the stigma of another in cross-pollination.

Pollen grains come in a wide variety of shapes, sizes, and surface markings characteristic of the species (see electron micrograph, right).

In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a partially differentiated dermis.

In a process called microsporogenesis, four haploid microspores are produced from each diploid pollen mother cell, after meiotic division.

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.

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).

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 transfer is frequently portrayed as a sequential process that begins with placement on the vector, moves through travel, and ends with deposition.

Entomophilous (literally insect-loving) plants produce pollen that is relatively heavy, sticky and protein-rich, for dispersal by insect pollinators attracted to their flowers.

[21] 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.

In northern Europe, common pollens for allergies are those of birch and alder, and in late summer wormwood and different forms of hay.

[26] 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.

[33] 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.

[35] Antihistamines are effective at treating mild cases of pollinosis; this type of non-prescribed drugs includes loratadine, cetirizine and chlorpheniramine.

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

[37] 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.

[38] Pollen may be valuable diet supplement for detritivores, providing them with nutrients needed for growth, development and maturation.

[40][41] 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.

The largest constituent is carbohydrates, with protein content ranging from 7 to 35 percent depending on the plant species collected by bees.

[44] 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[3] and from fungi and bacteria growth related to poor storage procedures.

[45] Pine pollen (송화가루; Songhwa Garu) is traditionally consumed in Korea as an ingredient in sweets and beverages.

[46] Māori of precolonial New Zealand would gather pollen of Typha orientalis to make a special bread called pungapunga.

[50][51] 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.

[55] Pollen has been used to trace activity at mass graves from the Bosnian War,[56] catch a burglar who brushed against a Hypericum bush during a crime,[57] and has even been proposed as an additive for bullets to enable tracking them.

[58] 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.