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Androecium – Definiton of Androecium and its Various Types
Third whorl of flower is the male reproductive part of the flower. It is composed of stamens (microsporophylls).
Each Stamen consist of 3 parts:
Upper swollen part with microsporangia.
Stalk of stamen
Tissue connecting anther lobes with filament
Anther typically contains two compartments 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.
Fusion of Stamens:
The fusion of stamens fusing among themselves or with other parts of flower. They are of two types.
- Connation and
Refers to the fusion of stamens among themselves. It is of 3 types:-
Filaments connate into one or more bundles but anthers are free. It may be the following types.
Filaments of stamens connate into a single bundle. Example: Malvaceae (Chinarose, Cotton).
Filaments of stamens connate into two bundles. Example: Fabaceae (pea) and Clitoria.
Filaments connate into many bundles. Example: Citrus, Bombax
Anthers connate, filaments free. Example: Asteraceae.
Filaments and anthers are completely fused. Example: Coccinea.
Refers to the fusion of stamens with other flral parts. Epipetalous: Stamens are adnate to petals. Example: Brinjal, Datura.
Stamens are adnate to sepals. Example: Grevillea (Silver oak)
b. Epitepalous (Epiphyllous):
Stamens are adnate to tepals. Example: Asparagus.
Connation product of stamens and stigma is called gynostegium. Example: Calotropis and Orchidaceae.
Pollen grains are fused together as a single mass Example: Calotropis
Arrangement of stamens relate to length of stamens:
Four stamens of which two with long fiaments and two with short filaments. Example: Ocimum
Six stamens of which four with long filaments and two with short filaments. Example: Brassica.
Stamens are of different lengths in the same flower. Example: Cassia.
One lobe with two microsporangia. They are kidney shaped in a cross section. Example: Malvaceae
It is a typical type, having two lobes with four microsporangia. They are butterfly shaped in cross section. Example: Solanaceae.
(Innate) Base of anther is attached to the tip of filament. Example: Datura.
Apex of filament is attached to the dorsal side of the anther. Example: Hibiscus.
Filament is attached to the anther at midpoint. Example: Grasses.
Filament is continued from the base to the apex of anther. Example: Nelumbo