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pollen

pollen, minute grains, usually yellow in color but occasionally white, brown, red, or purple, borne in the anther sac at the tip of the slender filament of the stamen of a flowering plant or in the male cone of a conifer. The pollen grain is actually the male gametophyte generation of seed plants (see reproduction). Inside the anther, pollen mother cells divide by meiosis to form pollen grains whose nuclei contain half the number of chromosomes characteristic of the parent plant. Each pollen grain contains two sperm nuclei and one tube nucleus. After successful pollination, the pollen germinates on the surface of the stigma of the pistil and produces a tube that grows down through the style to an ovule inside the ovary at the base of the pistil. The sperm nuclei are then discharged into the ovule; one fuses with the egg nucleus (see fertilization) and the other fuses with the polar nuclei to form endosperm (food-storage tissue) that in many cases nourishes the developing embryo in the seed. This process is basically similar in the conifers, except that in conifers there is no double fertilization and there may be a season's lapse between pollination and fertilization (see cone). Pollen grains, like sperms, are always produced in much greater quantities than are actually used, particularly by those plants that rely on the wind for pollination (e.g., grasses and conifers). Often clouds of dustlike pollen can be seen floating from wind-pollinated trees. Plants pollinated by insects and birds usually have sticky pollen and conspicuous flowers with colorful petals that often secrete perfume or nectar or both to attract the agents. Although pollen grains are microscopic in size and are thus visible to the human eye only in quantity, they are so diversified in appearance that plants are often identifiable by their pollen alone, e.g., by pathology. The waxy outer covering (which contains proteins and sugar—an additional attraction to pollen-gathering insects) is marked by characteristic patterns of ridges, spines, and knobs and is capable of expanding and contracting in the presence of moisture or dryness. Pollen grains are also remarkable for the length of the tubes some must produce: corn pollen tubes may grow 8 or 10 in. (20.3–25.4 cm) from the stigmas through the filamentous styles (commonly called "silk" ) to the ovaries. The life span of pollen may be less than two hours; its ability to produce the allergic reaction of hay fever continues indefinitely.

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"pollen." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pollen

"pollen." The Columbia Encyclopedia, 6th ed.. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pollen

pollen

pollen Yellow, powder-like spores that give rise to the male sex cells in flowering plants. Pollen grains are produced in the anther chambers on the stamen. When the pollen lands on the stigma of a compatible plant, it germinates, sending a long pollen tube down through the style to the ovary. During this process, one of its nuclei divides, giving rise to two male nuclei (the equivalent of male sex cells or gametes), one of which fuses with a female sex cell in fertilization. The other sex cell fuses with two more of the female nuclei to form a special tissue, the endosperm. In many species, this tissue develops into a food store for the embryo in the seed. See also alternation of generations; pollination

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"pollen." World Encyclopedia. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." World Encyclopedia. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/pollen

"pollen." World Encyclopedia. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/pollen

pollen

pollen The mass of grains containing the male gametes of seed plants, which are produced in large numbers in the pollen sacs. The pollen grains of insect-pollinated plants may be spiny or pitted and are usually larger than those of wind-pollinated plants, which are usually smooth and light. The pollen grain represents the male gametophyte generation; it contains two male nuclei: a generative nucleus and a tube nucleus. The wall of the mature pollen grain consists of the tough outer wall (exine) and the more delicate narrower intine. The latter gives rise to the pollen tube. See also pollination.

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"pollen." A Dictionary of Biology. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." A Dictionary of Biology. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-2

"pollen." A Dictionary of Biology. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-2

pollen grain

pollen grain A microspore in flowering plants, which germinates to form the male gametophyte, a structure made up of the pollen grain plus a pollen tube. The grain contains 3 haploid nuclei (a tube nucleus and 2 sperm nuclei), which pass down the tube to the ovum. One of the sperm nuclei fertilizes the ovum, and the second fuses with the 2 polar nuclei forming the endosperm. The tube nucleus (which is considered to be vestigial, having been completely functional earlier in the evolution of flowering plants) degenerates after double fertilization (so called because of the two unions of nuclei).

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"pollen grain." A Dictionary of Plant Sciences. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen grain." A Dictionary of Plant Sciences. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-grain-0

"pollen grain." A Dictionary of Plant Sciences. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-grain-0

pollen

pollen Collectively, the mass of microspores or pollen grains produced within the anthers of a flowering plant or the male cones of a gymnosperm. Different pollen types are described according to their shapes, apertures, etc. Furrows on the surface of the pollen grain are called ‘colpi’ (sing. colpus) or ‘sulci’ (sing. sulcus); the words are synonymous. Monosulcate pollen has a single colpus, tricolpate pollens have three, furrow-like colpi (sulci) arranged 120° apart, and there are many variants of this type.

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"pollen." A Dictionary of Ecology. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." A Dictionary of Ecology. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-0

"pollen." A Dictionary of Ecology. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-0

pollen

pollen Collectively, the mass of microspores (pollen grains) produced by the anthers of a flowering plant (angiosperm) or the male cones of a gymnosperm. Different pollen types are described according to their shapes, apertures, etc. Furrows on the surface of the pollen grain are called ‘sulci’ (sing, sulcus) and monosulcate pollen has a single sulcus. Tricolpate pollens have three, furrow-like, germinal apertures arranged 120° apart and there are many variants of this type.

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"pollen." A Dictionary of Earth Sciences. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." A Dictionary of Earth Sciences. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen

"pollen." A Dictionary of Earth Sciences. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen

pollen

pol·len / ˈpälən/ • n. a fine powdery substance, typically yellow, consisting of microscopic grains discharged from the male part of a flower or from a male cone. Each grain contains a male gamete that can fertilize the female ovule, to which pollen is transported by the wind, insects, or other animals.

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"pollen." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen-0

"pollen." The Oxford Pocket Dictionary of Current English. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen-0

pollen

pollen Collectively, the mass of microspores or pollen grains produced within the anthers of a flowering plant (angiosperm) or the male cones of a gymnosperm.

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"pollen." A Dictionary of Plant Sciences. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." A Dictionary of Plant Sciences. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-1

"pollen." A Dictionary of Plant Sciences. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-1

pollen

pollen †fine flour XVI; (bot.) powdery substance produced by the anther XVIII. — L. pollen flour, fine powder, rel. pulvis POWDER.

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"pollen." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen-1

"pollen." The Concise Oxford Dictionary of English Etymology. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen-1

pollen grain

pollen grain A microspore in flowering plants, which germinates to form the male gametophyte.

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"pollen grain." A Dictionary of Ecology. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen grain." A Dictionary of Ecology. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-grain

"pollen grain." A Dictionary of Ecology. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pollen-grain

pollen

pollenAlan, gallon, talon •raglan •biathlon, heptathlon, pentathlon, tetrathlon, triathlon •Guatemalan, Marlon •Ellen, felon, Magellan, Mellon, melon •Veblen • Declan • watermelon •Venezuelan • Elan •Anguillan, Dillon, Dylan, kiln, Macmillan, Milne, villain •limekiln • abutilon •pylon, upsilon •Hohenzollern, pollan, pollen, Stollen •Lachlan •befallen, fallen •chapfallen • crestfallen •Angolan, colon, Nolan, semicolon, stolen, swollen •kulan •woollen (US woolen) •sullen • myrobalan • gonfalon •castellan •ortolan, portolan •Köln, merlon

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"pollen." Oxford Dictionary of Rhymes. . Encyclopedia.com. 22 Jul. 2017 <http://www.encyclopedia.com>.

"pollen." Oxford Dictionary of Rhymes. . Encyclopedia.com. (July 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen

"pollen." Oxford Dictionary of Rhymes. . Retrieved July 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/pollen