Pollen Tube


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pollen tube

[′päl·ən ‚tüb]
(botany)
The tube produced by the wall of a pollen grain which enters the embryo sac and provides a passage through which the male nuclei reach the female nuclei.

Pollen Tube

 

a tubular outgrowth of a pollen grain that forms in seed plants after pollination. In its early development, it consists of a protuberance of the protoplast of the pollen grain. Covered with an internal membrane (intine), the tube emerges through a slender area of the pollen grain’s external membrane. In gymnospermous plants the pollen tube is formed in the pollen sac of the ovule; here it is embedded in the tissue of the nucellus. The pollen tube serves only as a haustorium (sucker) that receives nutrient matter (for example, in Cycadophyta and Ginkgo), or it ensures conduction of the male gametes to the female prothallium—the primary endosperm (in conifers and Gneticae).

In angiosperms the pollen grains form pollen tubes on the stigma of the pistil singly (in most plants) or in groups (in Malvaceae and Cucurbitaceae). The pollen tube, growing at its apex, emerges between the papillae of the stigma and then grows into the style and along the cells that line the stylar canal. If there is no canal, the tube grows between the cells of the stylar tissue, destroying the intercellular matter and, sometimes, the cells.

The pollen tube penetrates the ovule through the micropyle (porogamy) or, less frequently, through the chalaza (chalazogamy; in many Amentaceae) or laterally through the integument (mesogamy). In the female gametophyte—the embryo sac—the pollen tube usually enters between the egg cell and the synergid, or, upon destroying one of the synergids, it opens and releases the spermatozoids, after which double fertilization is possible.

A. N. SLADKOV

References in periodicals archive ?
Correlation between pollen diameter and rate of pollen tube growth in maize (Zea mays L).
These data suggest that the decline in pollen viability observed with glyphosate-treated GR plants corresponds to a decline in seeds per boll, perhaps because there was not enough viable pollen, capable of pollen tube formation, on the stigma.
Louisiana iris flowers have three stylar arms that fuse at the top of the ovary, allowing the measurement of conspecific and heterospecific pollen tubes growing in separate arms of a single flower.
Boron influences pollen germination and pollen tube growth in Picea meyeri.
The data obtained support the hypothesis that stigma excision can remove glycoproteins, and that pollen is able to germinate and start the pollen tube growth in the style tissues.
Data obtained from the in vitro germination tests indicated that the genotype, culture media and genotype x culture media interaction had significant effects on the germination of pollen grains and the length of the pollen tube of the castor bean (Table 2).
The effect of exogenous Ca ions on pollen grain germination and pollen tube growth-Investigations with the use of 45Ca21, verapamil, La31 and ruthenium red.
Pollen tube growth rates and the diversification of flowering plant reproductive cycles.
There are six phenotypic classes of pollen tube, five of them mutagen namely, balloon, wavy, branch, swollen, thin and only one is normal namely wildtype [43].
In Cretaceous flowers we've never before seen a fossil that shows the pollen tube actually entering the stigma," said George Poinar, Jr.
Sex for a plant happens when male pollen lands on the female part of a flower, called the stigma, and then grows a pollen tube down the style, which is attached to the stigma, to reach and fertilize an egg.
Viability of pollen and their pollen germination on stigma, pollen tube growth inside the style were noticed as favorable during third and fourth flashes.