Gynoecium: Definition, Structure, Placentation and Functions

The gynoecium in the structure of the flower represents the female reproductive organ in angiosperm plants. This female reproductive organ produces megaspores, which are involved in the production of female gametophytes. Different plant species have very different gynoecium arrangements and structures, which affect their reproduction and pollination. 

• Botanists use the term “Gynoecium” to refer to a “cluster of archegonia”. 
• It is one of the reproductive whorls that participates in sexual reproduction in flowers.
• Gynoecium is the site of both fertilization as well as seed development. 
• It consists of one or more pistils which are surrounded by the pollen-producing reproductive organs called the stamens.

In this article we will learn in detail about the structure of gynoecium as well as their functions.

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Structure of Flower

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A perfect flower consists of four parts and together they are called whorls. Calyx, corolla, androecium, and gynoecium are four whorls of a flower. Calyx and corolla are called accessory whorls. Androecium and gynoecium are called reproductive whorls. The different parts of the structure of the flower are discussed in detail below:

Calyx

Calyx represents the outermost whorl of flowers, which together constitute sepals. Sepals form a green leafy appearance and protect the floral shoot during the bud stage. When fully developed, calyx provides structural support to flowers.

Corolla

The corolla of the flower represents the collection of petals. With its bright-coloured appearance, it attracts insects for the process of pollination. Colorful petals are formed due to the presence of various pigments in the structure of the flower, such as anthoxanthin, anthocyanin, carotenoids, etc. Nectaries are small structures present in the petals that secrete sugar-rich substances called nectars. These nectars are pollen rewards to attract insects. 

​Androecium

The androecium is the male reproductive part of a flower. It is composed of stamens, an anther, a long, slender filament, and connective tissue. Each stamen is further divided into an anther and a filament. The androecium is responsible for the production of sperm cells packed inside pollen grains. 

Gynoecium

The gynoecium is the part of the angiospermic plant that gives rise to ovaries, which are transformed into fruit and seeds following sexual reproduction. The structure of gynoecium is represented by a collection of carpels or pistils.

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Structure of Gynoecium

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The gynoecium is the innermost female reproductive organ located at the center of the flower. It is the site in the plants where ovules are produced. The primary component of the structure of gynoecium is the carpel, which can be either apocarpous or syncarpous. The carpel of a gynoecium is further divided into style, stigma and ovary. 

• When a flowering plant consists of more than one carpel and is fused together, then it is called syncarpous.
• In the case of apocarpous, carpels are free in the angiosperm plant.
• The most common examples of apocarpous and syncarpous are rose and tomato, respectively.

Structure of Gyonecium

Stigma

The stigma is the topmost part of the flowering plant, forming the sticky part of the carpel.

• It receives pollen grains from the other and initiates fertilization.
• It consists of nutrient-enriched tissue that is used for the development of pollen tubes located in the ovule.
• During fertilization, the stigma recognizes the right pollen grains and acts as a surface for the germination of pollen. 

Style

Style is a long tube-like structure in the carpel that is helpful in pollen tube formation. 

• It is used to ensure the compatibility of pollen and initiate the process of fertilization. 
• This part of the structure of gynoecium is a connecting stalk between the stigma and the ovary. 
• Style acts as a pathway for male gametes to move toward the ovary and finally toward the ovule.

Ovary 

The final part of the structure of gynoecium is the ovary which is involved in the production of ovules or egg cells.

• It is the swollen part of the carpel that helps in the development of seed.
• Ovules, also known as megasporangia, protect the female gametes.
• It provides nourishment for the development of embryos located in the placental wall.
• The mature ovary is converted into fruit.

Also read: Difference between Carpel and Pistil

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Placentation

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Ovules developed in the ovary of a flower are arranged in a unique way, which is called placentation in a flower. On the basis of attachment, and development of ovules, various types of placentation are observed in a flowering plant, such as: 

• Axile Placentation: Axile placentation is a type of placentation in which the placenta is located at the axial (central) position. In this case, septa divide the ovary into more than one compartment, forming a multilocular ovary. The most common example of axile placentation is lemon.
• Parietal Placentation: The arrangement of ovules developing from either the inner walls or the peripheral segments of the ovary is called parietal placentation. Its most common example is mustard.
• Basal Placentation: When the development of placenta takes place at the base of the ovary, it is called basal placentation. The most common example of this structure of gynoecium is marigold.
• Marginal Placentation: Marginal placentation is the simplest type of placentation in which ovules are arranged in a row on the ventral suture of an ovary. Its most common example is the gram.
• Free Central Placentation: In free central placentation, the ovules are located at the central axis. Septa are absent in this type of placentation. Its most common examples include Dianthus and primrose.

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Hypogynous, Epigynous, and Perigynous Flowers

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A complete flower is often divided into three categories based on the position of the androecium, calyx, and corolla with respect to the ovary. 

Hypogynous Flowers

In a hypogynous flower, the structure of gynoecium appears on the top and ahead of all three whorls of a flower. Petals, sepals, and stamens are located at the receptacle below the gynoecium of these flowers. Its most common examples include hibiscus and brinjal. Hypogynous flowers are called superior ovaries.

Epigynous Flowers

A flower in which the structure of gynoecium lies below the calyx, corolla, and androecium is called an epigynous flower. It is also known as inferior ovary. The most common example of epigynous flowers is cucumber.

Perigynous Flowers

When all the whorls of a flower are located at the same level, it is called a perigynous flower. In these flowers, gynoecium is located at the centre of the flower, while other floral parts are located at the edge of the thalamus. It is also known as half-inferior ovaries. The most common examples of perigynous flowers are rose and peach.

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Functions of Gynoecium

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The gynoecium is the female reproductive part of a flowering or angiosperm plant. A plant has two reproductive whorls, one of them is the gynoecium which produces ovules before fertilization. After fertilization, the ovule develops into a seed which then leads to the development of fruits in plants. Following are some of the important functions of gynoecium in plants: 

1. Ovules Storage: The ovules, which become seeds after fertilization, are stored in the gynoecium.
2. Reproduction: By providing a location for pollen germination, it facilitates fertilization and pollination processes in plants.
3. Protection: The ovary, a component of the gynoecium, protects the ovum from mechanical damage and desiccation before fertilization.
4. Pollination: The receptive surface for pollen grains is the stigma, which is also a component of the gynoecium. 
5. Seed & Fruit Development: Following fertilization, the ovules become seeds and the ovary becomes the fruit.Through a variety of factors (such as wind, water, or animals), the fruit facilitates the dispersal of seeds.

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Things to Remember

• The gynoecium is the term used to represent the female reproductive part of the flowering part.
• It consists of one or more carpels which consist of ovaries that are converted into ovules.
• The four types of whorls in a flower include calyx, corolla, androecium and gynoecium.
• Placentation is divided into five categories, namely Axile, Parietal, Basal, free central and marginal placentation.
• A carpel or a pistil is composed of style, stigma, and ovary.