Home Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture Money Videos
conifer
Table of Contents
References & Edit History Quick Facts & Related Topics
Images
giant sequoia conifer heights Monterey pine lodgepole pine wind pollination Douglas fir Plate 4: Fleshy red appendages of fruits of the yew (Taxus), which attract birds. trees, deciduous and coniferous
For Students
conifer summary
Quizzes
Spreading oak tree in summer. (green, leaves, deciduous, shade)
Trees: Giants Holding the Sky
Field of baobab trees, Madagascar. (bottle tree)
Trees of the World
Venus's-flytrap. Venus's-flytrap (Dionaea muscipula) one of the best known of the meat-eating plants. Carnivorous plant, Venus flytrap, Venus fly trap
Plants: From Cute to Carnivorous
Read Next
Plant seedlings emerging from rich fertile soil
Do Plants Feel Pain?
Roses flowers plant colorful rose
Do Plants Have Sexes?
Majestic sequoias in Sequoia National Park. (trees; sunlight; forest; conifers; sequoia tree)
Saving the World’s Largest Trees
Discover
solar eclipse, sun, moon, astronomy, space
How Do You Tell the Difference Between Total, Annular, Solar, and Lunar Eclipses?
VAN, TURKEY - OCTOBER 25: A building and car ruined during the earthquake of Van-Ercis on October 25, 2011 in Van, Turkey. It is 604 killed and 4152 injured in Van-Ercis Earthquake.
What Is an Aftershock?
Black widow spider
9 of the World’s Deadliest Spiders
Queen Elizabeth II addresses at opening of Parliament. (Date unknown on photo, but may be 1958, the first time the opening of Parliament was filmed.)
All 119 References in “We Didn’t Start the Fire,” Explained
Adolf Hitler (Nazi, nazism, German leader).
9 Things You Might Not Know About Adolf Hitler
Pluto. The Changing Faces of Pluto. Most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003.
10 Important Dates in Pluto History
Solar eclipse of the sun.
The Sun Was Eaten: 6 Ways Cultures Have Explained Eclipses

Pollination

wind pollination
wind pollination
Windblown pollen from the male cone of a lodgepole pine (Pinus contorta).

All conifers are pollinated by wind. Pollen may be produced in enormous quantities, particularly by species of true pine (Pinus), which can blanket the surface of nearby lakes and ponds with a yellow scum of pollen (the pollen can cause allergies in humans). The pollen grains of many Pinaceae and Podocarpaceae have air bladders, which orient them in a pollination droplet exuded by the ovules so that, when the droplet is withdrawn back into the ovule, the pollen tube will penetrate the nucellus to the archegonium. The pollen grains of families that lack prothallial cells are more or less spherical, lack air sacs, and can extend a pollen tube anywhere on their surface so that precise orientation is unnecessary. Some conifers lack a pollination droplet mechanism. Douglas fir pollen grains land on an enlarged, stigmalike growth of the micropyle, from which the pollen tubes grow into the nucellus and archegonium. The pollen grains of the Araucariaceae land on the scales of the female cone, and the pollen tubes reach the micropyle by burrowing into the cone scales.

Fertilization and embryogeny

The processes of gametophyte growth and maturation in conifers is slow. The time from pollination to fertilization can exceed a year. After passing through the nucellus, the pollen tube presses between the neck cells of the archegonium and ruptures to release the tube nucleus, sterile cell, and the two male gametes (sperm). The ventral canal cell seems to help the male gametes enter the egg. One of the sperm fertilizes the egg nucleus to form the zygote, the first cell of the new sporophyte generation.

The conifer zygote has fewer free nuclear divisions than do Ginkgo or the cycads. While many divide twice to form four free nuclei in the centre of the egg cytoplasm, there may be from zero to six free nuclear divisions. The nuclei usually move away from the micropyle, and cell-wall formation accompanies further cell divisions. The embryo develops and is fed by the nutritive tissue of the female gametophyte. The embryo rapidly enlarges at the expense of the maternal tissue and initiates typical sporophytic organization, consisting at maturity of a single axis with a root apex at one end and a shoot apex at the other, surrounded by two to eight cotyledons.