Question

Can you please give a note on the parts of a typical flower?

Answer 1

Various parts and functions of a Typical Flower
The following are the important parts and their functions in a typical flower. Every part of the flower will serve a special function in it.
1. Bract
Below the base of a flower a scaly leaf like structure present is know as bract. A bract acts like an umbrella and protects the flower in bud condition from severe climatic conditions. A flower with bract is known as bracteate flower and without it is known as ebracteate flower. In Bougainvillea and Poinsettia plants, the flowers are provided with enlarged colorful bracts to attract insects for pollination.
2. Pedicel
A stalk like structure which connects a flower to the stem is known as pedicel. a flower with pedicel is known as pedicillate flower and the one which is directly attached to the stem without pedicel is known as sessile flower. A stalk of the flower is provided with the vascular tissue consisting of xylem and phloem to transport water and food materials in fluid form to the flower.
3. Thalamus
Thalamus or receptacle is a swollen or flat or dome-shaped or concave structure present at the tip of the pedicel. Thalamus is the structure on which all the floral parts arise or attached.

The floral parts of a flower are arranged on the thalamus in a ring like fashion called whorls. Usually there are four whorls of floral parts present in a typical flower. These whorls from outside of a flower to inside are Calyx (sepals), Corolla (petals), Androecium (stamens) and Gynoecium (carpels). Calyx and Corolla are known as non-essential whorls of a flower as they are directly involved in the process of reduction. Hence they are also known as the accessory organs of the flower. But Androecium and Gynoecium are known as essential whorls of the flower as they are directly involved in the sexual reproduction of the flower.
4. Calyx
Calyx is the outermost and first whorl of the flower. The individual members of calyx are known as sepals and are green in color. Colored sepals are present in Tamarindus. In Mussaenda plant a sepal in a flower is modified into an advertisement flag. In Asteraceae family, calyx in the flower is modified into pappus. In Brinjal (Solanum) sepals become persistant even after the formation of fruit. The important function of calyx in a flower is to hold all the floral parts together and also protect the flower in bud condition. As the sepals are green in color with chlorophyll, so we can expect they have the ability to carry out photosynthesis to some extent.

Usually in a flower five sepals are present but their number varies from one species of plant to the other. In some flowers, the margins of the sepals are fused with each other and such a condition is known as gamosepalous condition. In certain other flowers, the margins of the sepals are free from each other and such a condition is known as polysepalous condition. In certain flowers like Hibiscus (China rose), there is a second series of calyx also present for additional protection of the flower called Epicalyx.
5. Corolla
Corolla is the second whorl of a flower and the individual members of corolla are known as petals. The petals are differently colored with various colors and shades. The various colors of petals is due to various pigments present in the chromoplasts of these petals. The size, shape, color and number of petals present in the flower depends upon the nature of the flower. The important function of corolla in a flower is to attract insects for cross-pollination. For this along with bright color of the petals, the petals also emit scent smells as well as get modified into special shapes to attract insects.

Usually five petals are present in a flower but their number varies from one species of flower to the other. In some flowers, the margins of the flowers are fused with each other and such a condition is known as gamopetalous condition. Due to this condition the corolla will be bell shaped or tube shaped. In certain other flowers, the margins of the petals are free from each other and such a condition described as polypetalous condition.
6. Androecium
Androecium is the male reproductive part of a flower. It is the third whorl of a flower and the individual members of androecium are known as stamens. Each stamen is comprised of a long filament, a fertile anther and a connective. Filament and connective are non-fertile whereas anther is a fertile part. Anther is a two lobed structure which include four pollen chambers or pollen sacs inside. Pollen grains are produced inside the pollen sacs of the anther. Pollen grains are powdery dust like particles liberated from anther when the pollen sacs rupture. Each pollen grain on its surface is covered by rough wavy outer coat called exine for its protection and a smooth delicate inner lining called intine from which the pollen tube develops.
7. Gynoecium or Pistil
Gynoecium is the innermost whorl and female part of a flower. The individual members of gynoecium are known as carpels.
Structure of a Carpel
A carpel is made of three parts- ovary, style and stigma. Ovary is is the swollen basal part of the carpel. Ovary is divided into one or more chambers called locules. Each locule contain one or more round or egg shaped ovules in them. Each ovule encloses an embryo sac in it. An ovule after its maturation develops into a seed. Ovules are attached to a soft cushion like tissue in the ovary called placenta. The arrangement of ovules on the placenta of the ovary is known as placentation.

Style is an elongated tube like structure which connects stigma to ovary. When pollen grain germinates on stigma a tube like structure called pollen tube arises from arises from pollen grain which travels through the stylar canal and reaches the embryo sac. This pollen tube carries two male gametes to carry out fertilization in the embryo sac of ovule.

Stigma is the swollen, sticky tip part of the style which receives pollen grains during pollination process. This is the part where pollen grains also germinate. The stigma get variously modified like bilobed or globose or brush like or feathery in order to catch the pollen grains efficiently in different types of flowers.