A flower is a significant part of a plant; a modified shoot tailored for reproduction. In addition, it is an essential part of the bouquet, decorations, celebrations, garden, rituals, etc. Among different parts of a plant, the flower is the most attractive part due to its beauty and fragrance. Flower serves a significant function in plants. Let’s learn more about the essence of flowers in plants and its parts.
In a plant, flowers may grow either as a single flower or as a group. The inflorescence is defined as the arrangement of a cluster of flowers on a floral axis. The inflorescence is of two types, they are:
Racemose: In this type of inflorescence, the flowers branch laterally on the floral axis. Here the floral axis keeps on growing and the flowers develop in an acropetal pattern.
Cymose: In this type of inflorescence, the flower is the terminating point of each floral axis. In Cymose inflorescence, flowers follow the basipetal pattern of growth.
Types of Flowers
As we know, a flower constitutes the reproductive system of a plant. As the reproductive part, it ensures the continuance of a species of plant by the process called reproduction. A flower is composed of two accessory organs, calyx and corolla and of reproductive organs, androecium and gynoecium. All four whorls are arranged on a stalk called receptacle (thalamus).Flora can be categorized into many groups based on the number and arrangement of whorls, symmetry, floral appendages, etc.Based on the number of whorls, a flower can be unisexual or bisexual. A unisexual flower consists of the calyx, corolla, and androecium or gynoecium but in a bisexual flower, all the four whorls are present.
A flower can be classified as hypogynous, perigynous or epigynous depending on the position of three whorls- calyx, corolla, and androecium with respect to the ovary on the receptacle.
Hypogynous: In a Hypogynous flower, the ovary is superior to the other three whorls. Here the ovary is positioned high on the thalamus and other parts are below it, e.g., tomato, tulip, brinjal, etc.
Perigynous: In perigynous flower, the ovary is in the center and all four whorls are almost at the same level. Here, the ovary is half superior/ inferior, e.g., rose, peach, cherry, etc.
Epigynous: In epigynous flowers, the ovary is inferior to the other three parts. Here, the thalamus encloses the ovary inside it and the other three whorls are located above this, e.g., daffodil, cucumber, etc.
Parts of a Flower
A flower can be complete or incomplete. A complete flower consists of the following parts:
- Calyx: Calyx is the green colored part beneath the petals which protects the rising buds. It is the outermost whorl consisting of sepals. When sepals are united, it is called gamosepalous. In polysepalous, sepals are separated.
- Corolla: Corolla is the brightly colored part that attracts the pollinating agents for pollination. The members are called petals. The United and free petals are called gamopetalous and polypetalous respectively. Some flowers have fused petals-sepals termed as perianth.The pattern of arrangement of sepals or petals in a flower is called aestivation. Mainly there are four types of aestivation-valvate (e.g. Calotropis), twisted (e.g. China rose), imbricate (e.g. gulmohur) and vexillary (e.g. pea flower).
- Androecium: Androecium consists of the male reproductive organ called stamen. Stamen has two parts, namely: anther and filament which are usually yellow in color. Anther is a bilobed sac that produces and stores pollen whereas filament supports the anther. Arrangement and length of stamen vary from one flower to another.
- Gynoecium: Gynoecium, composed of the carpel, is the part that represents the female reproductive organ of a flower. It is composed of three parts- stigma, style, and ovary which are collectively known as a pistol. Stigma is the topmost part where the pollen lands. Then the pollen travels down through the style to the ovary. The ovary contains the ovules where the fertilization takes place and form seeds.
Within an ovary, ovules are arranged in different types, like marginal, axile, parietal, basal, central and free central. This pattern of arrangement of ovules in the ovary is called placentation.
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