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Stamen, the male reproductive organ of the flower, represents the third whorl of an angiospermic plant. Anther and filament are two components of the stamen. The anther splits or releases the pollen grains into the surrounding environment once they have grown to maturity.
Stamen
Key Highlights
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Key Terms: Stamen, Androecium, Anther, Pollen Grains, Male Gamete, Flowering Plants
What is Stamen?
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Stamen is a unit of androecium, which is one of the essential or reproductive whorls of flowering plants.
- The term "microsporangium" or "pollen mother cells" refers to the microspore that contains the pollen sac and generates pollen.
- Based on the type of plants, stamens can be attached to the floral axis or either one or all of the petals.
- It produces and releases pollen, which contains the male gametes used to fertilize the female gametes in the pistil.
- Stamens are used for the reproduction of seeds and help in the life cycle of angiosperms.
Parts of Stamen
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Stamen is a modified leaf-like structure which is further divided into two parts:
Anther
Anther is an important part of flowering plants, which stores and releases pollen grains at maturity.
- The thin, powdery substance called pollen, which is secreted by flowering plants, carries the male gamete of the flower.
- The two thecae found in this part of the stamen indicate that an anther is dithecous.
- It is derived from the Latin word anthera, which means medicine.
- Their size ranges from a fraction of a millimetre up to five inches.
- Anther forms a yellowish sac-like structure that can be attached to the base of the filament or throughout its full longitudinal axis.
Filament
The filament is made up of elongated cells and holds the anther in place. It is usually an extended, slender structure attached to the base of the flower. Filaments carry nutrients to the anther for the development of pollen.
Types of Stamen
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Based on the position and state of anther and filaments, stamen can be divided into the following types:
Polyandrous: A condition in which the stamens of flowering plants are free is called polyandrous condition. Example- Rose.
Monadelphous: When all the filaments of anther are fused together to form a single tube-like structure, then it is called the monadelphous stamen. In this case, filaments are free. Example- China Rose.
Diadelphous: In this type, stamens are united and arranged in two groups. Example- Pea plant.
Syngenesius: Syngenesius is a state in which only anthers are united while the filaments are free. Example- Sunflower.
Polyadelphous: In this case, stamens are arranged in the form of clusters or more than two groups. Example- Citrus Plant.
Synandrous: Synandrous refers to a condition in which both filaments and anthers are united. Example- Gourd.
On the Basis of Length
Stamens are divided into three categories on the basis of length:
Didymous: The type in which lengths of two filaments are equal is called didymous stamen. Example- Galium
Didynamous: In this state, four stamens are grouped into two equal pairs of different lengths in a flower. Example- Ocimum
Tetradynamous: In this case, the total number of stamen is six, with two short and four long. Example- Mustard
On the Basis of Attachment
Stamens are divided into four categories on the basis of length:
Basifixed: In this case, the filament is attached to the base of the anther. Example- Datura
Dorsifixed: When the dorsal portion of the anther is attached to the filament, it is called a dorsifixed anther. Example- Citrus
Adnate: In this condition, every part of the anther, from base to top, is covered in filaments.
Versatile: A versatile fixation is one in which the filament is affixed to the anther connective in a manner that permits the lobes of the anther to swing freely.
Functions of Stamen
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Stamen plays a crucial role in plant reproduction. The important functions are as follows:
- They consist of a stalk-like filament that helps in pollen dissemination via the microsporogenesis process.
- Stamen are used to transfer essential nutrients and water to the anther.
- The primary function of the anther, which is part of the stamen, is to produce pollen grains, which serve as the basis of sexual reproduction in plants.
Stamen Glossary
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Following are some important terminologies which are used in understanding the morphology of stamen.
- Staminode: Staminode is a flower that produces sterile stamens. Some of its examples include Cannonball Tree and Penstemon sp.
- Antipetalous: In this part, stamens are located opposite to the petals. Its example is primrose.
- Antisepalous: Antisepalous stamens are located opposite to the sepals. Its example is Murraya.
- Alternipetalous: In this case, stamens are found arranged alternately with the petals. Example is Primulaceae.
Sample Questions
Ques. What do you mean by pollination and pollinating agents? (2 marks)
Ans. The process by which pollen grains are transferred from the anther of the stamen to the stigma of carpel is called pollination. It usually occurs with the help of different means or agents which are called pollinating agents. Some of the examples of pollinating agents are as follows:
- Pollination by wind
- Pollination by bat
- Pollination by insects
- Pollination by birds
Ques. What are the differences between anther and stigma? (3 marks)
Ans. The difference between anther and stigma are as follows:
| Anther | Stigma |
|---|---|
| It is a part of a male reproductive part called the stamen. | It is a part of the female reproductive organ called the carpel or pistil. |
| Anther produces pollen grains which are transferred to stigma with the help of pollinating agents. | It receives the pollen grains and initiates the process of sexual reproduction in plants. |
| It is connected to a long, tube-like structure called filament. | It is attached to a tube-like structure called style. |
Ques. What are the different parts of a carpel or pistil? (1 mark)
Ans. Carpel is the unit of gynoecium which is a reproductive whorl of a flowering plant. It has three parts which are as follows:
- Style
- Stigma
- Ovary
Ques. What are nectaries? (2 marks)
Ans. Nectaries are small, nectar-producing structures that are present at the base of stamen. Nectars are food rewards produced by plants to attract pollinators such as birds and insects.
Ques. What do you mean by adhesion of stamens? (2 marks)
Ans. The attachment of stamen with either sepals or petals of a plant is called adhesion of stamen. There are two conditions of adhesion:
- Epipetalous- When the stamen is attached to the petals of a flower, then the condition is called epipetalous condition.
- Epiphyllous- In this type, the stamen is attached to the perianth of a flower, then the condition is called epiphyllous condition.
Ques. What do you mean by the cohesion of stamens? (2 marks)
Ans. Cohesion of stamen is a term used to describe the either free or fused state of stamen. Two conditions of cohesion are:
- Polyandrous- When the stamen are in the free state, it is called polyandrous condition.
- Monadelphous- The fused state of stamen is often referred to as a monadelphous condition. In this case, stamens are fused to form a bundle-like structure.
Ques. Describe the terms- exserted and inserted stamens? (2 marks)
Ans. Exserted stamens are those that most likely protrude from the flower when the filament is quite long. The stamen is said to be inserted when the filament is short enough that it stays within the flower.
Ques. Explain the adnate and basifixed conditions of anther? (2 marks)
Ans. Adnate refers to the state in which the filament is affixed to the backside of the anther across its whole length. Example- Mango.
- A situation known as "basifixed" occurs when the anther is joined to the filament from its base or when the filament terminates precisely at the end of the anther.
- Example is mustard.
Ques. What are pistillate & staminate flowers? (2 marks)
Ans. Flowers without androecium are called pistillate flowers. On the other hand, staminate flowers are those that contain only stamens. These are also called unisexual flowers due to the presence of only one reproductive organ.
- Example of pistillate flower- Squash
- Example of staminate flower- Eggplant
Ques. Do all plants with flowers undergo sexual reproduction? (2 marks)
Ans. Sexual reproduction can be observed only in angiosperms. The lack of reproductive structures in gymnosperms, or non-flowering plants, prevents them from participating in sexual reproduction.
Ques. What are microspores and megaspores? (2 marks)
Ans. Plants that flower are heterosporous. Two kinds of spores are mostly produced by them. Ovules produce megaspores, while anthers undergo meiosis to produce microspores. Later, megaspores become female gametophytes, while microspores develop into male gametophytes.
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