Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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Flower - a Fascinating Organ of Angiosperms

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  • Flower - a fascinating organ of angiosperms
  • A diagrammatic representation of the flower
  • Parts of a flower
  • Life span of flower

notes

Flower - a fascinating organ of angiosperms:

  • The reproduction process takes place in the plant via a special structure known as the flower.
  • Flowers are morphological and embryological marvels. 
  • The floral primordium undergoes hormonal and structural changes to form flowers.
  • Flowers can either be
    • Complete Flower - A complete flower is one that has calyx of sepals, corolla of petals, an androecium of stamens, and gynoecium of carpels (pistil).
    • Incomplete Flower - An incomplete flower is defined as a flower missing any of its main parts in its natural form, i.e., petals, sepals, stamens or pistils.
  • A complete flower consists of two different parts: the vegetative part and the reproduction part.

notes

Flower – Diagram:

A diagrammatic representation of the lateral side (L.S.) of a flower

notes

Parts of a flower:

The different parts of a flower are mentioned below:

A) Vegetative part of a flower:

The vegetative part of a flower consists of the calyx and corolla. The calyx and corolla are referred to as accessory whorls of the flower because they do not participate in the reproduction process but rather help it.

  1. Calyx - It is the outermost whorl of a flower. It consists of sepals, which are tiny green-coloured parts at the base of the flower. It protects the flower from any sort of mechanical injuries and desiccation. Some plants have coloured sepals the calyx are called petaloid. In many flowers, the sepals drop off at an early stage of development (i.e., before the flower even opens fully), they are known as caducous. Deciduous are the sepals that drop off after fertilization. The persistent sepals remain up to the fruiting stage. If the sepals are free the calyx is called polysepalous, and if they are united it is called gamosepalous.
  2. Corolla - It consists of petals of the flower. It is the second whorl of a flower. It attracts the pollinators which help to reproduce by transferring the pollen grain. It also protects the reproductive parts of a flower. Calyx and Corolla are collectively known as ‘perianth’.

(B) Reproductive parts of a flower:

The androecium and gynoecium are known as essential whorls because they are directly related to reproduction.
  1. Androecium - It is the male reproductive part of a flower, comprising stamens and it is the third main whorl of a flower. Each stamen comprises two parts, anther and filament. Anther is a bilobed (2 lobes) sac-like structure which is supported by the filament. The anther is an important part as it produces the pollen grains by performing meiosis. The filament is a long and slender stalk which is attached to the anther.
  2. Gynoecium - It is the female reproductive part of a flower. It is the fourth whorls of a flower situated in the central position of the thalamus. It consists of a pistil and its components are stigma, style, and ovary. The ovary is a chamber where the egg or ovule is stored for fertilization. Stigma is attached to the top of the carpel; it is the landing site of a pollen grain. Style is a tube-like structure that connects the ovary and the stigma. It transfers the pollen grain to the ovary.

notes

Life span of flower:

  1. Monocarpic plants: The plants in which flowering and fruiting take place only once in the whole life span are called monocarpic e.g., Annual & Biennial plants. Plants the annual and biennial types show clearcut vegetative/juvenile, reproductive and senescent phases, but in the perennial species,  
  2. Polycarpic plants: Polycarpic plants are those that flower and fruit multiple times during their life cycle, such as perennial plants. It is very difficult to clearly define life span phases in the case of perennial species.
    Exception: Monocarpic plants include bamboo, century plant (Agarerica Strothu kothiename perennial pists), and perennial pists. Bamboo species only flower once in their lives, usually after 50-100 years, produce a great number of fruits and die Strobilanthus kunthiana (Nezlakuranji) flowers only every 12 years. It flowered between September and October of 2006, transforming wide sections of hilly areas in Kerala, Karnataka, and Tamil Nadu into blue stretches and attracting a great number of tourists.
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