Parts of Flower - Essential Parts of Flower: Androecium

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Topics

  • Androecium: Male Reproductive Organ
  1. Male reproductive unit: Stamen
  2. Fusion of Stamens
  3. Anther types
  4. Anther attachment

Notes

Androecium: The male reproductive organ

Male reproductive unit: Stamen

  • The third whorl of flowers is the male reproductive part of the flower.
  • It is composed of stamens (microsporophylls).
  • A stamen is an angiosperm's male reproductive unit.
  • A typical stamen differentiates into three parts - Filament, Anther, and Connective.

Structure of Stamen
  1. Filament - The long and slender stalk is called the filament. The proximal end of the filament is attached to the thalamus or the petal of the flower.
  2. Anther - The anther is a bilobed structure with each lobe containing four pollen sacs or microsporangia. Anther typically contains two com­partments called thecae (singular theca). Each theca consists of two microsporangia. Two microsporangia fused to form a locule.
  3. Connective - Anther and filament are attached together with the help of a small region, called connective. Connective contains vascular tissues.
  • Sterile stamens are called Staminodes. Example: Cassia.
    (i) Distinct: stamens which do not fuse to one another.
    (i) Free: stamens which do not fuse with other parts of flower.
    (iii) Apostemonous: flowers with stamens that are free and distinct.

Notes

Fusion of Stamens:

  • The fusion of stamens fusing among themselves or with other parts of flower.
  • They are of two types - Connation and Adnation

1) Connation: Refers to the fusion of stamens among themselves. It is of 3 types - Adelphy, Syngenecious, and Synandrous.

  1. Adelphy: Filaments connate into one or more bundles but anthers are free. It may be the following types. 
    (i) Monadelphous: Filaments of stamens connate into a single bundle. Example: Malvaceae (China rose, Cotton).

    Monadelphous


    (ii) Diadelphous: Filaments of stamens connate into two bundles. Example: Fabaceae (pea) and Clitoria.

    Diadelphous


    (iii) Polyadelphous: Filaments connate into many bundles. Example: Citrus, Bombax

    Polyadelphous

  2. Syngenesious: Anthers connate, filaments free. Example: Asteraceae.

    Syngenesious

  3. Synandrous: Filaments and anthers are completely fused. Example: Coccinea.

2) Adnation: Refers to the fusion of stamens with other floral parts.

  1. Epipetalous: Stamens are adnate to petals. Example: brinjal, Datura.

    Epipetalous

  2. Episepalous: stamens are adnate to sepals. Example: Grevillea (Silver oak)
  3. Epitepalous (epiphyllous): stamens are adnate to tepals. Example: Asparagus.
  4. Gynostegium: Connation product of stamens and stigma is called gynostegium. Example: Calotropis and Orchidaceae.
  5. Pollinium: Pollen grains are fused together as a single mass. Example: Calotropis

Notes

Arrangement of stamens relate to length of stamens:

  1. Didynamous: Four stamens of which two with long filaments and two with short filaments. Example: Ocimum
  2. Tetradynamous: Six stamens of which four with long filaments and two with short filaments. Example: Brassica.
  3. Heterostemonous: stamens are of different lengths in the same flower. Example: Cassia.

Notes

Anther types:

  1. Monothecal: One lobe with two microsporangia. They are kidney-shaped in a cross-section. Example: Malvaceae

    Monothecal

  2. Dithecal: It is a typical type, having two lobes with four microsporangia. They are butterfly-shaped in cross-section. Example: Solanaceae.

    Dithecal

Notes

Anther attachment:

  1. Basifixed: (Innate) Base of anther is attached to the tip of filament. Example: Datura.


    Basifixed
     
  2. Dorsifixed: Apex of filament is attached to the dorsal side of the anther. Example: Hibiscus.

    Dorsifixed
  3. Versatile: Filament is attached to the anther at midpoint. Example: Grasses.


    Versatile
     
  4. Adnate: Filament is continued from the base to the apex of anther. Example: Nelumbo

    Adnate
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