Androecium

Essential Parts of Flower

Androecium

Androecium: Third whorl of flower is the male reproductive part of the flower. It is composed of stamens(microsporophylls). Each Stamen consist of 3 parts, a. Filament b. Anther c. Connective

Anther: Upper swollen part with mi-crosporangia.

Filament: Stalk of stamen

Connective: Tissue connecting anther lobes with filament

Anther typically contains two com­ partments called thecae (singular theca). Each theca consists of two microsporangia. Two microsporangia fused to form a locule.

Sterile stamens are called Staminodes. Example: Cassia. Distinct: stamens which do not fuse to one another. Free: stamens which do not fuse with other parts of flower. Apostemonous: flowers with stamens that are free and distinct. 

1. Fusion of stamens: 

Refers to the stamens fusing among themselves or with other parts of flower. Two types

Connation and 2. Adnation

1. Connation: Refers to the fusion of stamens among themselves. It is of 3  types.  a.  Adelphy.  b.  Syngenecious. c. Synandrous.

a. Adelphy: Filaments connate into one or more bundles but anthers are free. It may be the following types.

1. Monadelphous: Filaments of stamens connate into a single bundle. Example: malvaceae (chinarose,cotton).

2. Diadelphous: Filaments of stamens connate into two bundles.

Example: Fabaceae, pea.

3. Polyadelphous: Filaments connate into many bundles. Example: Citrus, Bombax

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

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

2. Adnation: Refers to the fusion of stamens with other floral parts. Epipetalous (petalostemonous): Stamens are adnate to petals .Example: brinjal,Datura. 

a. Episepalous: stamens are adnate to sepals. Example: Grevillea (Silver oak) Stamen

b. Epitepalous  Petal ( epiphyllous ) : stamens are adnate to tepals. Example: Asphodelus, Asparagus.

c. Gynostegium:Connation product of stamens and stigma is called gynostegium. Example: Calotropis and Orchidaceae.

d. Pollinium: Pollen grains are fused together as a single mass

2. Arrangement of stamens relate to length of stamens:

1. Didynamous (di-two, dynamis-strength): Four stamens in which two with long filaments and two with short filaments. Example: Lamiaceae, Ocimum. If all four stamens are in two equal pairs then the condition is called didynamous.

2. Tetradynamous(tetra-four): Six sta-mens of which four with long filaments and two with short filaments. Example: Brassi-caceae, (Brassica).

3. Heterostemonous: stamens are of different lengths in the same flower. Example: Cassia, Ipomoea.

3. Stamen insertion

1. Inserted: Shorter than the corolla tube and included within. Example: Datura.

2.Exserted:Longer than the corolla tube and project out.Example: Mimosa, Acacia arabica

The number of whorls of stamens present in a flower is called stamen cycly. Two major types are 1.uniseriate,a single whorl of stamens and 2.biseriate,two whorls of stamens.

4. Anther types

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

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

Someothertypes:

a) Haplostemonous: stamens are uniseriate and equal in number to the petals and opposite the sepals (antisepalous)

b)       Obhaplostemonous: Stamens are uniseriate, number equal to petals and opposite the petals (antipetalous)

c)        Diplostemonous: Stamens are biseriate, outer antisepalous, inner antipetalous. Example: Murraya.

d)       Obdiplostemonous: Stamens are biseriate, outer antipetalous, inner antisepalous.Example:Caryophyllaceae.

e) Polystemonous: Numerous sta-mens are normally many more than the number of petals.

5.    Anther attachment

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

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

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

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

6. Anther dehiscence

It refers to opening of anther to disperse pollen grains.

i       Longitudinal: Anther dehisces along a suture parallel to long axis of each anther lobe. Example: Datura, chinarose, cotton.

ii      Transverse: Anther dehisces at right angles to the long axis of anther lobe. Example: Malvaceae.

iii        Poricidal: Anther dehisces through pores at one end of the thecae. Example: Ericaceae, Solanum, potato, brinjal, Cassia.

iv. Valvular: Anther dehisces through a pore covered by a flap of tissue. Example: Lauraceae, Cinnamomum.

7. Anther dehiscing direction

It shows the position of anther opening relative to the anther of the flower.

1. Introrse: Anther dehisces towards the center of the flower. Example: Dianthus.

2. Extrorse: Anther dehisces towards pe-riphery of the flower. Example: Argemone.