We will define androecium. A typical flower is divided into 4 whorls. They are calyx, corolla, androecium and gynoecium. The androecium in the flower is the third whorl. It arises from the inner side of the corolla. The androecium is the male reproductive part of the flower. It is composed of stamens. A stamen is further composed of anther and filament. Anthers that are present inside the flower are generally bilobed. Thus, anther and stamens are the parts of androecium. Each lobe of the anther contains two microsporangia. They are also known as pollen sacs. Inside the pollen sacs, the pollen grains are produced. The staminode is the name given to a sterile staminode. The length of the filaments can vary in different flowers. Now we will learn more about the and roecium meaning, stamen, microsporangium and pollen grains.
The above paragraph helped us to define androecium. Stamens form the androecium. A stamen consists of anther and filament. The anther is a terminal bilobed structure. The filament is a long and slender stalk. The proximal end of the filament remains attached to the thalamus or the petal of the flower. An anther is a bilobed structure. A deep groove is present in front that separates the two anther lobes. The two anther lobes are attached by a band of tissues that are known as connective. An anther has a four-sided tetragonal structure. This structure consists of four microsporangia that are located at the corners. Two are present in each lobe. Therefore, a mature anther is tetrasporangiate. Pollen sacs are formed by microsporangia and on maturity, these microsporangia are filled with pollen grains. A microsporangium appears nearly circular in outline. Primary sporogenous cells are present in it. They are a homogenous mass of meristematic cells and are surrounded by another wall. They form the microspore mother cells.
This will help us to clearly understand and define androecium more. The anther is made up of 4 walls. They are:
This is the outermost layer of the anther. It is a single layer and serves the purpose of protection. Some plant species such as Arceuthobium develop fibrous thickening and they are known as exothecium.
Alpha-cellulose fibrous bands are present in the cells of this layer. These bands arise from inner tangential walls and they help in the dehiscence of the anther. This is because they are hygroscopic. In hydrophytes, these bands are absent.
These cells are ephemeral. This means that they are short-lived. They are 1-3 layered and degenerate at maturity.
This is the innermost layer of the anther wall. This layer surrounds the sporogenous tissue. The pollen grains receive nutrition from these cells. These cells have more than one nucleus and have dense cytoplasm. As these cells have more than one nucleus, so they are polyploid. There is also an increase in the DNA content of these cells. The increase in DNA content is achieved by Endomitosis, the Restitution nucleus and Polyteny. In endomitosis, there is DNA replication and the splitting of chromosomes. The restitution nucleus technique involves normal mitosis up to anaphase. The chromosomes at the two poles get surrounded by a nuclear membrane that is common to both. In polyteny, if the DNA replication is not supported by the splitting of chromosomes then polytechnic chromosomes are formed.
This is also known as glandular tapetum. Cells of these tissues secrete sporopollenin. They also secrete pollen kitt and compatibility proteins. These cells also provide ubisch bodies. The ubisch bodies help in the orientation of exine because they have a chemical called sporopollenin that is deposited upon them.
The cells of this layer undergo breakdown and because of this, the entire protoplasm moves towards the centre to serve the purpose of providing nourishment.
The sporogenous tissue is a group of compactly arranged homogenous cells. These are formed when the anther is young. This tissue occupies the centre of each microsporangium. Microsporogenesis is the process by which haploid microspores are formed from diploid microspore mother cells. These haploid microspores are then arranged in the form of four cells and are called microspore tetrad.
As we studied above, the pollen grains represent the male gametophyte or the androecium. The pollen grains are spherical structures and are about 25-50 micrometre in diameter. Sporoderm is the name given to their cell wall. This sporoderm consists of two layers that are the exine and the intine. The exine is the hard outer layer that is made up of sporopollenin. Sporopollenin is one of the most resistant organic materials. This layer can withstand high temperatures and even strong acids and alkalis. Till now, no enzyme that can degrade sporopollenin is known. This strong layer also helps in fossilization. This means that the pollen grains can be well preserved. This layer also protects the seed from various biotic and abiotic stresses. For the taxonomic significance, this layer also exhibits various patterns and designs.
Germ pore is the area where the sporopollenin is not present
The intine is the inner wall. It is a thin and continuous layer. It is made up of cellulose and pectin. The plasma membrane surrounds the cytoplasm of the pollen grain. The pollen grains of some species are also seen to cause pollen allergies. They are also responsible for causing bronchial afflictions. Some of the species of these pollens can also cause asthma and bronchitis. The pollen grains are rich in nutrients therefore they can be served as a food source. They are seen to cause an increase in the performance of athletes and horses. These pollen tablets are used as food supplements. Tablets and syrups of this pollen are also available in the market. Pollen viability is the period from which the pollens retain their ability to germinate on the landing of the stigma. This pollen viability also depends on temperature and humidity.
From the above paragraphs, we learned the meaning of androecium. Here we will learn about its types. There are mainly four types of androecium that are present in the flowers. They are
In this type of androecium, the stamens of the flower are free. Androecium of hibiscus is of this type.
In this type of condition, the filaments of the anther are fused to form one group.
In this type of condition, the filaments of the anther are fused into two groups.
In this type of condition, the filaments of the anther are fused to form more than one group.
Flowers are made up of four whorls of reproductive and non-reproductive components. The calyx, corolla, gynoecium, and androecium are among these.
Calyx: The outermost whorl is made up of sepals, which are usually green, leaf-like structures.
Corolla: A whorl of petals that are often brilliantly coloured.
Androecium: Male reproductive organs called stamens are found in the third whorl.
Gynoecium: Female reproductive components termed carpels make up the innermost whorl.
The non-reproductive structures of a flower are the calyx and corolla, whereas the reproductive structures are the androecium and gynoecium. Egg cells are produced by the gynoecium, while sperm cells are produced by the androecium. The structure of the androecium will be the subject of this lesson.
Let's take a closer look at the androecium's various sections.
The androecium is divided into stamens. Stamens or stamina are the plural forms of the word. Multiple stamina make up an androecium; each one is made up of two parts: the filament and the anther.
The word filament has been derived from the Latin word ‘filum’, which means ‘thread’. In reality, the filament is a synonym for the thread. A tiny wire called a filament is heated to high temperatures in an incandescent light bulb that is devoid of oxygen to prevent the filament from catching fire while it is heated. The filament glows as it starts to light up. The original filaments were constructed of carbon, but due to their high melting point, tungsten is now commonly used.
A flower's stamen, or pollen-producing component, is made up of a slender stalk called a filament and an anther.
The stamens of the vast majority of angiosperms include separate pollen-containing components called anthers. Thecae (singular theca) are two compartments in anthers, each of which contains two microsporangia (the fusion product of which is a locule)(Anthers are frequently tetrasporangiate as a result.) The connective tissue, which connects and connects the two thecae, is where the filament (if existent) is attached. Pollen grains, the immature male gametophytes of seed plants, are produced in microsporangia.
This is the anther wall's deepest layer. The sporogenous tissue is surrounded by this layer. These cells provide sustenance to the pollen grains. These cells have several nuclei and a lot of cytoplasms. These cells are polyploid because they have more than one nucleus. In addition, the DNA content of these cells has increased. Endomitosis, Restitution nucleus, and Polyteny all contribute to the increase in DNA content. DNA replication and chromosome splitting occur during endomitosis. Normal mitosis up to anaphase is used in the restoration nucleus procedure. The chromosomes at both poles are encased in a nuclear membrane that is the same for both. Polytechnic chromosomes are generated when DNA replication is not supported by chromosomal splitting in polyteny.
Polyandrous: Polyandrous refers to a condition in which a flower's stamens are unattached.
Monadelphous: Monadelphous is a condition in which the filaments of anthers in a flower are fused into one group.
Diadelphous: Diadelphous is a condition in which the filaments of anthers in a flower are fused into two groups.
Polyadelphous: When the filaments are fused in more than two groups, the condition is said to be Polyadelphous.
1. What are the Different Types of Androecium?
There are several types of androecium based on how the stamens and filaments are. These types are polyandrous, monadelphous, and diadelphous. Polyandrous is that type of androecium when it has free stamens and they're not united. In the case of a monadelphous androecium, a group of stamens is not free but is united by their filaments while the anther is free. Similarly in diadelphous androecium, the filaments are united in two bundles and are not free.
2. What is a Stamen and What is it Composed of?
Stamen is an important part of a flower as it takes part in reproduction. It is the male reproductive part of a flower and consists of a long thin structure called 'stalk' and a filament that has an anther at the tip of it. The anther is responsible for producing the pollens which take part in pollination and it consists of four saclike structures where these pollens are made.
3. How can I Study Androecium?
To learn about the various terms related to androecium and to study the different concepts related to it, you can refer to the above article. In this article, we have discussed the different types of the androecium, its different layers and what it is used for. This article will help you to completely understand all the stuff related to androecium as all the topics have been structured beautifully. To know more about this topic, download the Vedantu app now!
4. What Do You Understand by Adhesion and Cohesion of Stamens?
Adhesion means the attachment of the stamen. In this condition, the stamen may get attached to the other floral organs such as petals and sepals. When they are attached to the petal, they are called epipetalous. When the stamen is attached to the perianth, it is called epiphyllous. The cohesion of stamens means that they may be free or united. Polyandrous is the name given to them when they are free. When they are united in a single bundle, they are called monadelphous. When they get united and form two bundles, they are known as diadelphous. Polyadelphous is the condition when they get united and form more than one bundle.
5. What Do You Understand by Aestivation?
Aestivation is the mode of arrangement of petals and sepals. These sepals and petals are arranged in the floral bud. There are four types of aestivation:
Valvate: In this type of arrangement, the sepals and the petals are present in a whorl. They just touch each other and no overlapping takes place.
Twisted: Here in this aestivation, the sepal and petals of one flower overlap the sepals and petals of the other flower. The overlapping is present in a particular direction.
Imbricate: The sepals and petals are also attached in this type but not in a specific pattern.
Vexillary: In this arrangement, the largest of the petals/sepals overlaps the two smaller petals/sepals and then these two overlaps the other two or more present.
Flowers are a fascinating part of all plants and these are important for the survival of plant species as it is flowers that take part in reproduction. Here, in this article, we are going to talk about the male reproductive part of a flower i.e., androecium.