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Advert: Buy Gold

Pollen

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SEM image of pollen grains
Pollen grains from a variety of common plants:
sunflower (
Helianthus annuus), morning glory (Ipomea purpurea),
hollyhock (
Sildalcea malviflora), lily (Lilium auratum), primrose
(
Oenothera fruticosa), and castor bean (Ricinus communis''). ''

Pollen is a fine powder consisted of microspores (pollen grains), which are the male gametes of higher plants. Pollen is produced in the microsporangium (antherss of an angiosperm flower). Pollen grains come in a wide variety of shapes, sizes, and surface markings characteristic of the species (see photomicrograph at right). Most, but certainly not all, are spherical. Pollen grains of pines, firs, and spruces are winged. The smallest pollen grain, that of the Forget-me-not plant (Myosotis sp.), is around 6 μm (0.006 mm) in diameter. The study of pollen is called Palynology and is highly useful in paleontology, archeology, and forensics.

The transfer of pollen grains to the female reproductive structure (carpel in angiosperms) is called pollination.

Allergy to pollen is called hay fever. Generally pollens that cause allergies are those of anemophilous (literally wind-loving) plants, which produce very lightweight pollen grains in great quantities for wind dispersal, and subsequently contacting human nasal passages through breathing. Anemophilous plants generally have inconspicuous flowers. Entomophilous (literally insect-loving) plants produce pollen which is relatively heavy and sticky, for dispersal by insect pollinators.

Honeybee with collected pollen
Honeybee carrying pellet of pollen in its corbicula
In the US, people often falsely blame the conspicuous entomophilous goldenrod flower for allergies. Since this pollen does not become airborne, only way to get goldenrod pollen on your nasal passages would be to stick the flower up your nose. The late summer and fall pollen allergies are usually caused by ragweed, a common, anemophilous and inconspicuous flower. Arizona was once regarded as a haven for people with pollen allergies, since ragweed does not grow in the desert. However, as suburbs grew and people began establishing irrigated lawns and gardens, ragweed gained a foothold and Arizona lost its claim of freedom from hay fever. Anemophilous spring blooming plants such as oak, hickory, and pecan; and early summer grasses may also induce pollen allergies. Cultivated flowers are most often entomophilous and do not cause allergies.

The "tapping panel dryness disease" of the rubber plant is caused by a virus transmitted on pollen grains.

Pollen is sold as a nutritional supplement, marketed as "bee pollen" (even though it is of course from flowers).

External Links

image:pollen.arp.300pix.jpg
Clumps of yellow pollen on a flower head
(Larger version)


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