Pollen tube

Pollen tube

The pollen tube of most seed plants acts as a conduit to transport sperm cells from the pollen grain, either from the stigma (in flowering plants or angiosperms) to the ovules at the base of the pistil, or directly through ovule tissue in some gymnosperms (conifers and gnetophytes). In other gymnosperms ("Ginkgo" and cycads) the pollen tube is involved only in nutrient uptake from ovule tissue by the pollen grain, and does not convey sperm cells to the egg.

In angiosperms the pollen tube germinates from the pollen grain and grows the entire length through the stigma, style, ovary and ovules to reach the eggs. In maize, this single cell can grow longer than 12 inches to traverse the length of the pistil. The sperm cells by themselves are not motile and are carried within the tube. As the tip of the tube reaches an egg it bursts and releases two sperm cells leading to a double fertilization. One sperm unites with the egg cell to produce the embryo of a new plant, while a second sperm unites with the "central cell" to produce the endosperm of the seed. The endosperm is rich in starch, proteins and oils and is a major source of human food (e.g., wheat, barley, rye, oats, corn)

Lipids at the surface of the stigma stimulate pollen tube growth for compatible pollen. Plants that are self sterile inhibit the pollen grains from their own flowers from growing pollen tubes. The presence of multiple grains of pollen has been observed to stimulate quicker pollen tube growth in some plants.

The number of pollen grains needed for pollination/syngamy is equivalent to the number of ovules. One can look at a cut watermelon to identify the mature seeds that resulted from syngamy, and the white, undeveloped seeds that resulted from a failure of syngamy. The proportion of mature seeds to undeveloped ones is proportional to the quality of the fruit, which can then be tested by taste.

The trace mineral boron is vital to pollen tube growth. While too much boron is toxic, a complete lack of boron in the soil can cause a crop failure.

Ferns, algae, and even some seed plants (including "Ginkgo biloba" and cycads) do not have their pollen directly deposited to the egg through pollen tubes: they have flagellate sperm, which swim through a watery fluid to pollinate the egg cells.

External links

* [http://www.alpine-plants-jp.com/himitunohanazono/ebine_himitu_1.htm Images : Pollen tetrad and Pollen tube] " Calanthe discolor" Lindl. - Flavon's Secret Flower Garden


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Look at other dictionaries:

  • Pollen tube — Pollen Pol len, n. [L. pollen fine flour, fine dust; cf. Gr. ?] 1. Fine bran or flour. [Obs.] Bailey. [1913 Webster] 2. (Bot.) The fecundating dustlike cells of the anthers of flowers. See {Flower}, and Illust. of {Filament}. [1913 Webster]… …   The Collaborative International Dictionary of English

  • pollen tube — n. Bot. the tubelike growth that emerges from a germinating pollen grain and enters the embryo sac in an ovule: a male gamete passes through it to fertilize the female gamete …   English World dictionary

  • pollen tube — pollen tube. См. пыльцевая трубка. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • pollen tube — noun (botany) a slender tubular outgrowth from a pollen grain when deposited on the stigma for a flower; it penetrates the style and conveys the male gametes to the ovule • Topics: ↑botany, ↑phytology • Hypernyms: ↑plant part, ↑plant structure *… …   Useful english dictionary

  • pollen tube — Spermatophyta Sper ma*toph y*ta, n. pl. [NL.; spermato + Gr. ? plant.] (Bot.) A phylum embracing the highest plants, or those that produce seeds; the seed plants, or flowering plants. They form the most numerous group, including over 120,000… …   The Collaborative International Dictionary of English

  • pollen-tube — dulkiadaigis statusas T sritis augalininkystė apibrėžtis Siūliška, mezginės link tįstanti dygstančios žiedadulkės išauga, kuria vyriškosios gametos plaukia prie sėklapradžio. atitikmenys: angl. pollen tube rus. пыльцевая трубка …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • pollen tube — pol′len tube n. bot the tube that forms from a germinating pollen grain and grows toward the ovule, carrying male gametes with it • Etymology: 1825–35 …   From formal English to slang

  • pollen tube — noun Date: 1835 a tube that is formed by a pollen grain and conveys the sperm nuclei to the embryo sac of an angiosperm or the archegonium of a gymnosperm …   New Collegiate Dictionary

  • pollen tube — Bot. the protoplasmic tube that is extruded from a germinating pollen grain and grows toward the ovule. [1825 35] * * * …   Universalium

  • pollen tube — noun the tube that develops from the wall of a pollen grain and, in seed plants, provides a passage through which the male nuclei reach the embryo sac to effect fertilization …   Wiktionary

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