F L O W E R S

Angiosperm Flower Structure and Function

Angiosperm Definition

A plant that has flowers and produces seeds enclosed within a carpel. The angiosperms are a large group and include herbaceous plants, shrubs, grasses, and most trees.

Angiosperm Flower Structure

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Pistil

The Pistil, is the female reproductive part of a flower. It is the female organs of a flower, comprising the stigma, style, ovary, and ovule (more information below). Pistils are typically located in the center of the flower and are surrounded by petals, sepals and stamens. Some flowers, such as the sweet pea, have one simple pistil, while others, including larkspur, have more than five pistils. The pistil typically sticks out beyond the stamens, or a flower's male organs, so that insects can easily brush up against the pistil. This helps transfer pollen and fertilize the seeds in the ovaries.
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Stigma

Stigma is one of the female parts of the flower. Stigmas have a sticky top that allows the pollen to stick and pollinate the plant. Without pollination, there would be no seeds. It is the sticky bulb that you see in the center of the flower, it is the part of the pistil of a flower which receives the pollen grains and on which they germinate. Since the stigma is the receptacle for pollen, it has a sticky surface that the pollen adheres to and transports the pollen to the ovum for fertilization. The pollen may be captured from the air (wind-borne pollen, anemophily), from visiting insects or other animals (biotic pollination), or in rare cases from surrounding water (hydrophily).
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Style

A style is a female part of the flower. It is a long, slender stalk that connects the stigma, which it sits on top of, to the ovary. It also protects the the stigma. A style plays an important role as the pollen grain germinates on the stigma. It creates a pollen tube, which it will use to burrow through the entire length of the style. The style is very important during the fertilization process because not only is it the location where the pollen tube forms, but it is also involved in stopping incompatible pollen from penetrating the ovary. When the pollen tube starts to extend within the style, genetic information is exchanged between the pollen and the plant. At this time, the plant also creates a toxin. Style carries the stigma and exposes it properly for pollination.
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Ovule

In seed plants, the ovule is the a female reproductive part that produces the gamete - egg. It is the part of the ovary that becomes the seed. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument(s) forming its outer layer(s), the nucellus (or remnant of themegasporangium), and female gametophyte (formed from haploid megaspore) in its center. After fertilization, the ovule develops into a seed. In angiosperms (flowering plants), one or more ovules are enclosed by the ovary (portion of the carpel, or female reproductive organ). Each ovule is attached by its base to the stalk (funiculus) that bears it. A mature angiosperm ovule consists of a food tissue covered by one or two future seed coats.
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Ovary

The part of a plant, usually at the base/bottom of the flower, that has the seeds inside and turns into the fruit that we eat (if it were a fruit). Ovaries are large, bulbous structures located at the base of the pistil. The ovary contains ovules. The ovaries are usually located in the well-protected center of the flower, although this can vary depending on the species. The ovaries act as a kind of protective chamber around the fragile undeveloped ovules, which develop into seeds from which new plants grow. The female ovary is attached to the male stigma by a tube known as the style, through which pollen is transferred in order to fertilize ovules stored in the ovary. Once the ovules have been fertilized and developed into seeds, the ovary can act as a vehicle to disperse the seeds in order for them to germinate. The terminology of the positions of ovaries is determined by the insertion point, where the other floral parts (perianth and androecium) come together and attach to the surface of the ovary.


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Stamen

The male reproductive part of a flower is referred to as the stamen. The stamen (plural stamina or stamens) is the pollen-producing reproductive organ of a flower. A stamen typically consists of a stalk called the filament and an anther which contains microsporangi. (see below for more details). The number of stamen is usually the same as the number of petals. The main function of the stamen is to produce the pollen grains, which house male gametes, or sex cells, necessary for reproduction.
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Anther

The anther is the part of the stamen where pollen is produced and contained. The anther is located within the stamen where these gametes are created. It is the yellow, pouch-like part inside of the flower that holds pollen grains and is usually on top of a long stalk that looks like fine hair. It is composed of a long tube, called a filament, and has a pollen-producing structure on the end. It is crucial in the reproduction of flowering plants, as it produces the male gametophyte, known as pollen.

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Filament

This is the stalk that holds the anther and attaches it to the flower. The filament is the fine hair stalk that supports anther to make it accessible to insects. This fine hair-like stalk is where the anther sits on top of.
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Petal

Petals are modified leaves that surround the reproductive parts of flowers. Petals are what give a flower its unique shape, and are often brightly colored to attract insects and critters, which unwittingly aid in the fertilization of ovules through pollination. Flower petals come in a wide variety of shapes and colors, from pale pinks to vivid oranges. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals. Petals have various functions and purposes depending on the type of plant. In general, petals operate to protect some parts of the flower and attract/repel specific pollinators. The pretty colors and pleasant fragrance of flower petals draw the attention of pollinating insects, birds and other animals. So basically they assist in pollination.
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Sepal

Sepals are modified leaves that form the outer whorl of a flower. They are typically green but can be other colors. Flowers have different numbers of sepals depending on the species. Collectively, the sepals are called the calyx of the flower. Sepals are the external covering of flower bud. It is to protect the flower before it opens/blossoms and often is the support for the petals when in bloom. After flowering, most plants have no more use for the calyx which withers or becomes vestigial. Some plants retain a thorny calyx, either dried or live, as protection for the fruit or seeds.
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Receptacle

The receptacle is the thickened part at the bottom of the flower which holds its major organs and part of a stem from which flower organs grow. This is the part of a flower stalk where the parts of the flower are attached. It also keeps the flower in an elevated position so as to attract the insects. base of flower.
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Pedicel

A pedicel is a stem that attaches a single flower to the inflorescence (complete flower head). A pedicel is a short flower stalk in an inflorescence or cluster of flowers. Pedicels hold individual flowers in place, but how they do that depends on the form of the inflorescence. The function of pedicels is to expose flowers to the sun and wind and put them in a position so their aroma and color attracts pollinating insects more easily.
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Song of the Parts of the Flower

Parts of Flowers Song

Angiosperm Life Cycle

Angiosperm (flowering plant) Life Cycle