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Androecium – Definition, Components, Structure, Functions

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  • Last Updated : 03 Jun, 2022
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Reproduction is a biological process in which living organisms produce offspring similar to them. Reproduction is an important event to ensure the continuity of species on earth. In sexual reproduction, there is a chance of evolution due to mutation, linkage, etc. which is necessary for adapting and surviving to the changing environment and climate. The flower is the reproductive unit in most sexually reproducing plants. A flower consists of 4 whorls. These whorls are arranged circularly one after the other on the thalamus. Four whorls are:

Calyx: This is the outermost whorl offer flower which consists of sepals and usually is green.
Corolla: Corolla is the collection of petals of a flower. It is usually colorful or brightly colored to attract pollinators for pollination.
Androecium: An androecium is the male reproductive part of the flower.  
Gynoecium: Gynoecium is the female reproductive part of the flower. 

Androecium

An androecium is present in the third whorl of the flower. It is a male reproductive part of a flower. It contains pollen grains, which are responsible for reproduction in the male part of the plant. Male gametes of a flower are the pollen grains. Androecium which is also called stamen consists of filament, anther, and connective tissue.  

Androecium Components

Androecium consists of a knob-like bilobed structure anther, a long slender structure filament, and a connective tissue that holds the anther and filament together. Sometimes if the stamen is not developed properly and if it remains sterile, then that sterile stamen is called a staminode (Example: Cassia and Carina).

Androecium

Flower

Anther

Anther is the topmost part of an androecium. Anthers have two sack-like structures called lobes. These lobes are connected with the help of connective tissue. Each lobe is called anther lobe. In each lobe, there will be two chambers. These chambers are called microsporangium which consists of microspores that further develop into pollen grains. Each anther will have four microsporangia. These microsporangia produce microspores, which are also called pollen grains.

Filament

The filament is a long, slender, or tube-like structure on which anthers or the spore will be present. On some rare occasions, few species of plants will not be having filament on their flower. This condition is called a sessile condition (Example: Arum and Maculatum). If the filament is very long, then stamens are most likely to project out of the flower. This condition is termed as the exserted stamen. In some cases, the filament is very short, and the stamen remains inside the flower this condition is known as the inserted stamen.

Based on how the filament is attached to the stamen, it is classified as follows

  1. If the anther is present in continuation with the filament, this condition is called adnate.  Example: Magnolia and water lily
  2. When the anther is attached from its base to the filament or if the filament ends just at the end of the anther, it is called Basifixed. In simple terms, the filament is connected to anther, just by the base. Example: Mustard 
  3. If the filament is attached to the back of the anther, it is termed dorsifixed. The anther is attached dorsally to the filament. Example: Sesbania 

Connective

A connective is a tissue that connects two anther lobes. The connective might be minimal in some species, as in Euphorbia. This condition is known as Discrete.

A stamen of flowers may be united with petals or among themselves on this arrangement basis flower are divided into 2 subtypes

  1. Epipetalous: It’s a condition where stamens are attached to the petals. Example: Brinjal, datura
  2. Epiphyllous: It’s a condition where stamens are attached to the perianth and petals are united. Example: Lily

 Four conditions of the Androecium in flowers

  1. Polyandrous: It’s a condition where the stamens of a flower remain free. Example: Petunia.
  2. Monadelphous: It’s a condition where stamens are united into one bundle or stamens are fused together by the filaments to form a single bundle. Example: Hibiscus, cotton, china rose
  3. Diadelphous: It’s a condition where stamens are united to form two bundles or filaments of stamens are fused to form two groups or bundles. Example: Pea, bean
  4. Polyadelphous: It’s a condition where stamens are united to form more than two bundles or filaments of stamens in a flower are fused to form more than two groups or bundles. Example: Citrus, castor

Internal structure of Anther

T. S of Anther

 

From the morphology of anther, we can see that the anther is having knob-like bilobed structure, both the lobes being connected by connective tissue. If we try to have a look at a transverse section of an anther, it is having four chambers, called thecae. in the transverse section, we can divide the cells of a theca as peripheral primary parietal cells and inner primary sporogenous cells.

Parietal cells

The Parietal cells are further divided into outer endothecium and middle layers.

  1. Outer endothecium: During mitosis, the parietal cell undergoes cell multiplication and which can be differentiated as outer endothecium, a single layer of cells, whose functions are required at the dehiscence of anther.
    The epidermis acts as a protective layer that provides strength to the structure. The crucial gaseous exchange between an anther and surrounding happens through this epidermis.
  2. Middle layer: 1 to 3 layers of parenchymous cell tissue are formed just immediately to the outer endothecium called the middle layer.
    It is the second layer situated below large endothecium cells. The middle layers are used to store starch which mobilizes pollen grains during maturation.

Sporogenous cells 

These are the cells that are going to develop into actual cells. These cells are generated through meiosis.

  • Inner tapetum: The inner tapetum is made up of the outer endothecium and middle layer. It is having pyramid-shaped cells which exhibit a radial arrangement around the spores. It is the last layer of an anther. It is a nutrient-rich layer that nourishes the pollen grains during development. It contains hormones that encourage the growth of pollen grain. It will contain a compatible protein that will ensure germination on only the right pollination.

Important Functions of Anther

  • Dehiscence of pollen grains- When the pollen grains are completely developed, the anther splits or throws out pollen grains into the atmosphere. Then, through the process of pollination, these polling rains are carried to the gynoecium of a flower. These pollen grains will carry both biological and genetic information that is required for the growth of a new seed or plant. These pollen grains will carry both biological and genetic information that is required for the growth of a new seed or plant. The dehiscence involves the bursting of a fully developed anther that contains enormous energy, which will help following grains travel hundreds of meters distance. The dehiscence of pollen grains and capturing of pollen grains by gymnasium will happen simultaneously to ensure a successful fusion of male and female gametes.
  • Pollination- It is an important process that takes place in flowers during reproduction. The transfer of pollen from the anther to the gynoecium is carried out with or without the help of some external agents called pollinators. Flowers contain a few attractive things like Aroma food etc. which will attract pollinators to flowers. So many human activities, the habitat of small organisms, can also cause successful pollination. Some important pollinators are air, wind, insects, birds, water, etc.

Conceptual Questions

Question 1: Define androecium. 

Answer : 

The androecium is the male reproductive part of the flower. It lies in the third whorl of the flower. Androecium consists of stamens. Each stamen represents the male reproductive organ. Male gametes of a flower are the pollen grains. Androecium which is also called stamen consists of filament, anther, and connective tissue. 

Question 2: Define epipetalous and give an example. 

Answer : 

Epipetalous is a condition where stamens are attached to the petals.  
Example: Brinjal

Question 3: What are Adnate and Besifixed anthers? Give examples. 

Answer : 

  • The condition where the filament is attached throughout the length, at the back of the anther is termed as adnate.
    Example: Magnolia and water lily
  • The condition where the anther is attached from its base to the filament or if the filament ends just at the end of the anther is termed Basifixed.
    Example: Mustard

Question 4: Define exerted and inserted conditions of stamens. 

Answer:

Exserted: When the filament is very long, stamens likely project out of the flower, such stamens are termed as exserted. 
Inserted: When the filament is short and the stamen remains inside or within the flower it is termed as inserted.

Question 5: What is an anther? 

Answer:

Anther is the topmost part of an androecium. Anthers have two sack-like structures called lobes. These lobes are connected with the help of connective tissue. Each lobe is called anther lobe. In each lobe, there will be two chambers. These chambers are called microsporangium which consists of microspores that further develop into pollen grains. Each anther will have four microsporangia. These microsporangia produce microspores, which are also called pollen grains.

Question 6: What is the dehiscence of pollen grains?

Answer:

When the pollen grains are completely developed the anther splits or throws out pollen grains into the atmosphere. Then through the process of pollination, these polling rains are carried to the gynoecium of a flower. The dehiscence involves the bursting of a fully developed anther that contains enormous energy, which will help following grains travel hundreds of meters distance.

Question 7: What is pollination? Why is it necessary? 

Answer : 

The transfer of pollen from anther to the gynoecium is carried out with or without the help of some external agents called pollinators. This process is called pollination. Pollination is necessary to ensure the successful fusion of male and female gametes. It also ensures no pollen contamination meaning transfer of pollens of one species to the same species of gynoecium. 


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