Question

$\star\;{\underline{\underline{\sf{\pink{QuesTion\;:}}}}}$

What is a flower?
Describe the parts of a typical Angiospermic flower.
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Answer 1

AnsWer :

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

1) Pedicel:

• 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).

2) Thalamus:

• 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.

3) Floral whorls:

• 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.

a) Calyx:

• 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.

b) Corolla:

• 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.

Perianth:

• 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).

c) Androecium:

• 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.

d) Gynoecium:

• 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).

Answer 2

Answer:

$\huge\bold\star\rm{Question}$

1) What is a flower?

What is a flower?Describe the parts of a typical Angiospermic flower.

$\huge\rm\pink{\underline{\underline{Answer}}}$

1) What is a flower?

Ans:- The flower is the reproductive part of a plant. To understand how a flower helps in the sexual reproduction in plants,let us study a typical flower.

${\fbox\color{blue}{stalk}}$

• The flower is attached to the shoot by means of stalk or pedicel. The tip of the stalk is enlarged and slightly flattened, from where, the petals and other part arise. This flattened part of the stalk is called the thalamus.

The four whorls of the flower are –

${\fcolorbox{lime}{lime}{calyx}}$

• This is the outermost part of the flower forming a whorl of tiny green leaf-like structures called sepals. In the bud condition, they enclose the inner parts of the flower providing them necessary protection.
• Sepals are the green, outermost part of the flower

${\fcolorbox{lime}{lime}{corolla}}$

• Corolla is made up of petals, it forms the second inner whorl arranged next to the sepals. Usually, petals are white or coloured but rarely green. The petals make the flower attractive.
• Petals are the large, fragrant and brightly coloured parts of the flower.

${\fcolorbox{lime}{lime}{androecium(the \: male \: part)}}$

• It is the third whorl, inner to the petals, consisting of delicate thread-like structures called stamens. Each stamen is formed of a long, narrow, thin filament and a broad sac-like bilobed anther found at its tip.
• Stamens are the male reproductive part of the flower.

${\fcolorbox{lime}{lime}{gynoecium(the \: female \: part)}}$

• It consists of carpels, the fourth innermost part of the flower. It is also called a pistil. Each carpel is formed of three parts – a swollen ovary at the base, a narrow thread-like style in the middle and a terminal expanded stigma at the top.
• Carpels are the female reproductive part of the flower.