from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Botany A minute opening in the ovule of a seed plant through which the pollen tube usually enters.
- n. Zoology A pore in the membrane covering the ovum of some animals through which a spermatozoon can enter.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. In seed-bearing plants, a small opening in the integuments of the ovule through which sperm are able to access the ovum.
from the GNU version of the Collaborative International Dictionary of English
- n. An opening in the membranes surrounding the ovum, by which nutrition is assisted and the entrance of the spermatozoa permitted.
- n. An opening in the outer coat of a seed, through which the fecundating pollen enters the ovule.
from The Century Dictionary and Cyclopedia
- n. In botany, the orifice or canal in the coats of the ovule leading to the apex of the nucleus, through which the pollen-tube penetrates.
- n. In zoology: The scar or hilum of an ovum at the point of its attachment to the ovary
- n. Any opening in the coverings of an ovum through which spermatozoa may gain access to the interior, or a cluster of minute pores on the surface of an egg through which fertilization is effected. On the eggs of lepidopterous insects these pores often form a rosette at one end.
- n. In zoology: In certain sporozoans, a minute opening in the oöcyst through which the microgamete enters to fertilize the macrogamete.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. minute opening in the wall of an ovule through which the pollen tube enters
This opening is called the "micropyle," and allows the pollen tube to enter.
* (* Little as a name may actually affect the facts, we ought certainly to confine the name "micropyle" to canals of the egg-membrane, which serve for the entrance of the semen.
The receptive part of the gymnosperm ovule is called the micropyle.
For small quantities of seed, cut through the seedcoat opposite the micropyle, or pointed-end of the seed, taking care not to damage the seed embryo.
To avoid damaging the seed embryo, cut or scrape the seedcoat opposite the micropyle.
The seed should be sown 1-2 cm deep with the micropyle pointing downwards; the emerging root is not strongly geotropic and may come up out of the soil if the seed is planted upside down.
Then when it lies on the stigma it develops a long tube, which passes down the style and through the micropyle of the ovule to the germinal vesicles, one of which is fertilized by what is probably an osmotic transference of nuclear matter.
Amici's subsequent (1846) discovery of the entrance of the pollen-tube into the micropyle, fertilizing the female cell which then develops into the embryo.
Fertilization: takes place when a spermatozoön enters through the micropyle of an ovum and unites with the cell nucleus: loosely applied like copulation or to its completion.
In _Casuarina_, _Juglans_ and the order Corylaceae, the pollen-tube does not enter by means of the micropyle, but passing down the ovary wall and through the placenta, enters at the chalazal end of the ovule.