Flowers and pollen are essential to the reproductive function of plants. Pollen carries the male sex cells of the plant, which are produced on a structure called the stamen or androecium, often known more descriptively as the filament. The stamen contains a number of different parts that are used to facilitate reproduction.
Botanists use the term filament more specifically to refer to the thin stalks that support the pollen-producing anthers. In most flowers, the filaments are easily seen and arise from the center of the flower. The filament serves a structural purpose to the reproduction of the plant by extending the anthers and making the pollen more accessible to pollinating animals, such as hummingbirds and honeybees.
The top of the filament is the home to the anther, a larger and usually slightly elongated knob that is often coated with yellow, dusty pollen. Inside each anther are four sacs in which pollen is produced. Anthers contain the developed pollen, making it available to be carried by the wind or picked up by a pollinating animal.
The microsporangia, the sacs in the anther, are packed with cells called mother cells that are instrumental in the development of pollen. The mother cells undergo a process called meiosis in which the cell's genetic material is divided among four different cells. Each cell is bound by a thick wall that will protect the pollen grain when it is finished. These cells now replicate, each forming three cells--two sperm cells and a tube cell that will deliver the sperm to the egg during fertilization--that constitute a single pollen grain. When the anther splits open, the pollen is exposed to the air ready to be carried to the female parts of the flower.
Pollen is the ultimate product of the male parts of the flower. As noted above, each pollen grain contains male sex cells and, when the pollen lands on the female parts of a flower, the tube cell grows and extends down into the flower until it reaches the ovary. When the tube cell bursts, it releases the two sperm cells, one of which forms the infant plant while the other combines with other female cells to form a nutritive substance called endosperm that will nourish the seedling as it develops. Pollen is visible on the heads of the filaments, or anthers, and carries easily on the wind and clings to the bodies of pollinating animals, allowing plants to reproduce with individuals at a considerable distance from them, resulting in increased genetic diversity.
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