Social Sciences, asked by Ruhianka56829, 9 months ago

#What is a flower? Describe the parts of a typical angiospermic flower.

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Answered by ashugupta2280

Answer:

Answered by Anonymous

Flower: Flower is defined as a highly

modified and condensed shoot with limited

growth and specialized for sexual reproduction in higher plants.

Sometimes a flower grows in the axil of a leaf-like structure known as the bract.

A typical flower has the following three parts.

i. Pedicel

ii. Thalamus

iii. Floral whorls

The stalk of the flower is called pedicel which projects the flower for pollination
A flower with pedicel is called pedicellate flower or a stalked flower and flower without pedicel is known as non-pedicellate flower or sessile flower.
It is generally an elongated, cylindrical and green structure.
In some flowers, a small leaf-like structure called bract may also be found on the pedicel.
A flower having a bract is known as bracteate flower (Clitoria, Hibiscus) and the one without a bract is called an ebracteate flower (Lily).

The upper, swollen, condensed, knob-like part of the pedicel is called thalamus. It is also called receptacle or torus.
It is differentiated into nodes, in which the floral whorls are inserted and internodes, that are highly condensed
Thalamus consists of four compactly arranged nodes and three highly condensed internodes.

A circle of modified floral leaves is called a floral whorl.
A typical dicotyledonous flower has four floral whorls namely calyx, corolla, androecium and gynoecium.
They are arranged in concentric manner with calyx as outer and gynoecium being the innermost whorl.
A flower with all the four whorls is described as a complete flower and the flower having the absence of one or more floral whorls is called an incomplete flower.
Among these, calyx and corolla are called accessory whorls or helping whorls of the flower.
The androecium and gynoecium are called essential whorls or reproductive whorls.

Calyx is the outermost, accessory whorl of the flower.
It's individual member or unit is called sepal. The sepals are usually small and green.
When the sepals are free from each other, the condition is termed as polysepalous calyx. e.g. Brassica
When the sepals are united, it is termed as gamosepalous calyx, e.g.China rose.

Corolla is the second accessory whorl of the flower present on the inner side of the calyx.
Its individual member or unit is called petal.
The petals are usually brightly coloured and fragrant.
When the petals of the corolla are free from each other, the corolla is called polypetalous corolla, e.g. Rose
When the petals are united, it is known as gamopetalous corolla.e.g. Datura.

When the members of accessory whorls of a flower are not differentiated into sepals and petals, it is called perianth.
In such flowers, the floral members are identical in shape, size and colour.
Each member of perianth is called a tepal.
Tepals of the perianth may be free (polyphyllous perianth) or united (gamophyllous perianth).

Androecium is the third essential and male reproductive whorl of the flower.
It consists of individual members or units called stamens or microsporophylls.
Each stamen consists of a filament, connective and anther.
The filament projects the anther to facilitate dispersal of pollen grains.
The anther is fertile part of the stamen which is usually bilobed.
Each anther lobe contains two microsporangia filled with microspores or pollen grains at maturity.
Hence, the anther is bilobed and tetrasporangiate.
An anther with two microsporangium is called two celled or dithecous (Datura),while anther with a single microsporangium is called one-celled or monothecous (Hibiscus).
Connective is the cementing tissue which connects the anther lobes and the filament together.

Gynoecium is the fourth, innermost and female reproductive whorl of the flower. Its individual member or unit is called a carpel or megasporophyll.
Each carpel consists of three parts: ovary, style and stigma.
The ovary is basal, hollow, swollen, fertile part of the carpel. Its cavity is called ovarian cavity or locule.
The cavity bears one or more ovules attached to the placenta.
The mode of arrangement of ovules on placenta in the ovary is called placentation. The style is middle, narrow, elongated, sterile part of the carpel which connects ovary with the stigma.
The stigma is the terminal part of the carpel which receives pollen grains during pollination.
Therefore, it becomes sticky at maturity. It also facilitates germination of pollen grains.
Gynoecium is also called pistil. It may be simple (monocarpellary) or compound (polycarpellary).

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