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Art connection

 Illustration shows parts of a flower, which is called the perianth. The corolla is composed of petals, and the calyx is composed of sepals. At the center of the perianth is a vase-like structure called the carpel. A flower may have one or more carpels, but the example shown has only one. The narrow neck of the carpel, called the style, widens into a flat stigma at the top. The ovary is the wide part of the carpel. Ovules, or megasporangia, are clusters of pods in the middle of the ovary. The androecium is composed of stamens which cluster around the carpel. The stamen consists a long, stalk-like filament with an anther at the end. The anther shown is tri-lobed. Each lobe,  called a microsporangium, is filled with pollen.
The four main parts of the flower are the calyx, corolla, androecium, and gynoecium. The androecium is the sum of all the male reproductive organs, and the gynoecium is the sum of the female reproductive organs. (credit: modification of work by Mariana Ruiz Villareal)

If the anther is missing, what type of reproductive structure will the flower be unable to produce? What term is used to describe an incomplete flower lacking the androecium? What term describes an incomplete flower lacking a gynoecium?

If all four whorls (the calyx, corolla, androecium, and gynoecium) are present, the flower is described as complete. If any of the four parts is missing, the flower is known as incomplete. Flowers that contain both an androecium and a gynoecium are called perfect, androgynous or hermaphrodites. There are two types of incomplete flowers: staminate flowers contain only an androecium, and carpellate flowers have only a gynoecium ( [link] ).

 Illustration shows parts of a corn plant. Pistillate flowers are tiny flowers that cluster in strands to form the tassel at the top of the plant. Pollen grains are small, teardrop-shaped structures. Carpellate flowers are clustered in the immature ear, which is covered by leaves. Silk protrudes from the tops of the leaves covering the flower. In the mature ear, the kernels form where the carpellate flowers were located.
The corn plant has both staminate (male) and carpellate (female) flowers. Staminate flowers, which are clustered in the tassel at the tip of the stem, produce pollen grains. Carpellate flower are clustered in the immature ears. Each strand of silk is a stigma. The corn kernels are seeds that develop on the ear after fertilization. Also shown is the lower stem and root.

If both male and female flowers are borne on the same plant, the species is called monoecious (meaning “one home”): examples are corn and pea. Species with male and female flowers borne on separate plants are termed dioecious, or “two homes,” examples of which are C. papaya and Cannabis . The ovary, which may contain one or multiple ovules, may be placed above other flower parts, which is referred to as superior; or, it may be placed below the other flower parts, referred to as inferior ( [link] ).

 Part A shows a lily, which has an ovary above the petals. The ovary sits above the teardrop-shaped petals. Part B shows several fuchsia flowers hanging down from a stem. The ovary is below the edge of the petals.
The (a) lily is a superior flower, which has the ovary above the other flower parts. (b) Fuchsia is an inferior flower, which has the ovary beneath other flower parts. (credit a photo: modification of work by Benjamin Zwittnig; credit b photo: modification of work by "Koshy Koshy"/Flickr)

Male gametophyte (the pollen grain)

The male gametophyte develops and reaches maturity in an immature anther. In a plant’s male reproductive organs, development of pollen takes place in a structure known as the microsporangium    ( [link] ). The microsporangia, which are usually bi-lobed, are pollen sacs in which the microspores develop into pollen grains. These are found in the anther, which is at the end of the stamen—the long filament that supports the anther.

 Illustration A shows cross section of an anther, which has four lobes each containing a pollen sac, or microsporangium. Inside the pollen sac is a layer called the tapetum, and within this ring are the microspore mother cells. As the microsporangium matures, two pollen sacs merge and an opening forms between them so that the pollen can be released. Micrographs in part B show pollen sacs with a visible opening between them.
Shown is (a) a cross section of an anther at two developmental stages. The immature anther (top) contains four microsporangia, or pollen sacs. Each microsporangium contains hundreds of microspore mother cells that will each give rise to four pollen grains. The tapetum supports the development and maturation of the pollen grains. Upon maturation of the pollen (bottom), the pollen sac walls split open and the pollen grains (male gametophytes) are released. (b) In these scanning electron micrographs, pollen sacs are ready to burst, releasing their grains. (credit b: modification of work by Robert R. Wise; scale-bar data from Matt Russell)

Questions & Answers

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Eveline Reply
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Lwitiko Reply
outline the significance of mitosis to organisms
Lwitiko
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Eveline
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Oreva
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James
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Cosmo
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tissue combined to form organ
zameer
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Elishs
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Elishs
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Kags
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Harleen
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Bernard
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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