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Pollen tube
 
 
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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
Ginkgo

Ginkgo , frequently misspelled as "Gingko", and also known as the Maidenhair Tree after Adiantum, is a unique species of tree with no close living relatives....
 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.






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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
Ginkgo

Ginkgo , frequently misspelled as "Gingko", and also known as the Maidenhair Tree after Adiantum, is a unique species of tree with no close living relatives....
 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. Like ferns, other basal land plants, and many algae, these gymnosperms have flagellate sperm, which swim through a watery fluid to fertilize the egg cells.

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
Maize

Maize , known as corn in some countries, is a cereal domesticated in Mesoamerica and subsequently spread throughout the American continents....
, 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
Endosperm

Endosperm is the tissue produced in the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain Vegetable oils and protein....
 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)

Lipid
Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
s 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
Pollination

Pollination in flowering plants and gymnosperms is the process that transfers pollen, which contain the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself....
/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.

See also

  • Aperture (botany)
    Aperture (botany)

    Apertures are very small spots on the walls of a pollen, where the wall is thinner and/or softer. For germination it is necessary that the pollen tube can reach out from the inner of the pollen and transport the chromosomes to the egg deep down in the Carpel....


External links


  • Calanthe discolor Lindl. - Flavon's Secret Flower Garden