A flower is the reproductive structure of angiosperm that facilitates sexual reproduction. It consists of sepals that enclose and protect the developing bud, followed by colorful petals that attract pollinators and the male and female reproductive part. The primary function of the flower is reproduction in plants, attracting pollinators for fertilization and producing seeds and fruits. They also play a role in genetic diversity and adaptation.
What is a Flower?
A flower is the reproductive structure found in flowering plants (angiosperms). It consists of two main parts: the male reproductive part called stamens, which consist of a filament and an anther that produces pollen, and the female reproductive part known as the pistil or carpel, consisting of the stigma, style, and ovary where ovules are present. These parts help in pollination and sexual reproduction in flowering plants.
Flowers can be classified into two main categories: complete and incomplete. A complete flower possesses all four whorls of parts—sepals, petals, stamens, and pistils. A complete flower consists of two different parts: Vegetative Part and Reproductive Part. On the other hand, an incomplete flower lacks one or more of these structures.
Diagram of Flower
A well labelled diagram of the flower is as follows:
Parts of a Flower
The flower normally has four whorls, which are divided into essential whorl and accessory whorl. Essential whorl comprises gynoecium and androecium whereas Accessory whorl comprises Calyx and Corolla. The different parts of a flower are as follows:
Vegetative Part of a Flower
The vegetative part of a flower includes the sepals and petals, which are primarily involved in protecting the developing bud and attracting pollinators, respectively. These components are not directly related to the reproductive function of the flower but contribute to its overall structure and function. They are defined as follows:
- Sepal: Sepals are the outermost, usually green, leaf-like structures of a flower that protect the developing bud.
- Petal: Petals are the typically colorful, modified leaves of a flower that surround the reproductive parts of a flower and help to attract pollinators.
Reproductive Part of a Flower
The reproductive part of a flower consists of the stamens and the pistil (or carpel). Stamens are the male reproductive organs, producing pollen containing male gametes. The pistil is the female reproductive organ, containing the stigma, style, and ovary, where the female gametes (ovules) are located. These parts play a central role in pollination and fertilization, ensuring the plant’s reproduction.
Whorls
In a flower, there are mainly four whorls of floral parts. The outermost whorl is the calyx, composed of sepals; the next is the corolla, made up of petals; followed by the androecium, which contains the stamens; and finally, the innermost whorl is the gynoecium, containing the pistil or carpel. These whorls collectively define the flower’s structure and reproductive components. These four whorls are as follows:
Calyx
The outermost green protective whorl of the plant is known as calyx. Unit of the calyx is sepal. The initial layer in the flower structure is calyx. They are said to be modified leaves. Hence, the collection of sepals is called the calyx. The sepal or calyx is green in colour and its chief function is to protect the flower. The calyx may be gamosepalous ( sepals united) or polysepalous ( sepals free). It encloses the unopened bud. They perform a protective role for the flower earlier than it opens and afterwards put forth from the base of the flower.
Modifications of Calyx
- Spiny Calyx: When calyx gets modified in the form of spines. These are spiny calyx. Example- Trapa bispinosa (water chestnut) the calyx is spinous in the fruit.
- Persistent Calyx: When calyx remains attached to the fruit is called the persistent calyx. Example – Brinjal and tomato. Solanaceae family shows persistent calyx.
- Leafy Calyx: Sometimes calyx converts into a leaf-like structure and is called the leafy calyx. Example- Mussaenda.
Corolla
Corolla is the second accessory whorl a flower made up of petals. The collection of petals is known as Corolla. It is just beneath the calyx. petals are usually brightly coloured to attract insects for pollination calyx and corolla together forms the perianth,the non-reproductive portion of the flower. The corolla may be gamopetalous (petals united) or polypetalous (petals free). corolla varies greatly in plants with shape and colour. It may be tubular-shaped, funnel-shaped or wheel-shaped.
Types of Corolla
- Cruciform-When four petals in a flower are separated. It is a type of polypetalous corolla and is the characteristic of the family Brassicaceae. It is a regular corolla. Hence, the cruciform corolla is found in radish and mustard.
- Rosaceous-When 5 petals of a flower are spread. Hence, rosaceous corolla is found in roses which have corolla of 5 broad petals.
- Bell Shaped-Bell-shaped corolla is called campanulate. In this type, the corolla is present in the bell-shaped structure .example – campanula, and physalis.
Functions of Corolla
- Pollination-Since corolla is the attractive part of a flower and the petals are brightly coloured .moreover, it releases an aromatic smell which catches the insect’s attention like birds, bees, etc those help in the pollination of the flower and is known as pollinating agents.
- Protection of essential Whorl-Corolla protects the essential whorl i.e androecium and gynoecium ,the reproductive parts of a flower that participate in the fertilisation of the flower to produce fruit.
- Storage Part-Petals function as the storage house of sugar-rich nectar, attracting pollinating agents .
- Reproduction-Corolla directly does not take part in pollination but helps to attraction pollinating agents and perform pollination .its main function is to assist in the reproductive process of a plant.reproduction in plants occurs by the method of pollination.
Androecium
The androecium is an essential whorl of the plant and it is considered as Male Reproductive Organ of the plant. It consists of stamen each of which consists of an anther and filament which produces pollen grain. Collectively the stamens form the androecium. Pollen grains are produced in pollen- sacs. A sterile stamen is called Staminode. It is a sterile flower which cannot participate in reproduction. For example Caesalpinioideae family.
When stamens are attached to the petals,the condition is called Epipetalous. Example-Brinjal. or Epiphyllous, when stamens are attached to the perianth. Example: Lily.
Function of Androecium
- Production of Pollen Grains: Its main function is to produce microspores i.e, pollen grains containing male gametes within anther lobe. androecium serves the purpose of fertilisation in flowering plants.
- Pollination: Androecium consists of stamens which have 2 parts: anther and filament. anther helps to protect, store and produce pollen grain and the filament holds the anther up. these parts help the pollinating agents to perform pollination.
Gynoecium
The gynoecium is the second essential whorl of the plant or the innermost whorl and is considered a Female reproductive organ of the plant. It is surrounded by the androecium. the structural unit of gynoecium is Carpel. It consists of three parts Stigma, Style and Ovary. when more than one carpel is present, they may be free and are called Apocarpous. Example: Rose and lotus. They are termed Syncarpous when carpels are fused. Example: Mustard and tomato.
Parts of Gynoecium
- Stigma: Stigma is a receptive surface of gynoecium for receiving pollen grain. it is at the tip of the style.
- Style: Style is a tube-like structure in which the way of pollen grains move towards the ovary.
- Ovary: Lower swollen part of gynoecium is known as ovary. The ovary consists of the ovule and within the ovule, embryosac is present where double fertilisation takes place.
Function of Gynoecium
- Fertilization: Fertilisation takes place in the gynoecium. the gynoecium develops into seeds and fruits after fertilisation.
- Protection: Gynoecium plays an important role in producing and protecting ovules.
Functions of Flower
The function of the flower are as follows:
- The primary function of a flower is to facilitate the reproduction of the plant by producing seeds through pollination and fertilization.
- Flowers use their colors, fragrances, and nectar to attract pollinators such as bees, butterflies, birds, and insects, which aid in the transfer of pollen between flowers.
- Sepals, the outermost part of a flower, protect the developing bud from damage, harsh weather, and herbivores
- Flowers facilitate the process of fertilization by bringing together pollen from the stamens to the stigma of the pistil, allowing for the fusion of male and female gametes.
- After successful fertilization, flowers develop seeds within the ovary, which can later be dispersed for the growth of new plants.
- Flowers contribute to biodiversity by supporting a wide range of pollinators and providing essential resources for various species within ecosystems.
- Some flowers, such as those of fruit-bearing plants, develop into fruits that protect and nourish the seeds, making them more appealing to animals for dispersal.
Also read: Sexual reproduction in plants
FAQs on Parts of a Flower and their Functions
1. What are the Important Parts of a Flower?
The important parts of a flower are sepal, petals, the stamens (male reproductive organs) and the pistil (female reproductive organ), which collectively facilitate pollination and reproduction in flowering plants.
2. How do Flowers Reproduce?
Flowers reproduce through pollination, where pollen containing male gametes is transferred to the stigma of the pistil. Fertilization occurs when the male and female gametes fuse, leading to seed development.
3. What is the Function of a Flower?
The chief function of a flower is to serve in pollination by attracting pollinating agents like bees, birds, etc. flower is a bright coloured attractive structure of flowering plants.
4. What Determines Whether a Flower is Bisexual or Unisexual?
A flower is considered bisexual if it contains both androecium (stamens) and gynoecium (pistil). A unisexual flower has either stamens or carpels exclusively, making it either male or female.
5. How are Complete and Incomplete Flowers Different?
Complete flowers have all four whorls of floral parts (sepals, petals, stamens, and pistils), whereas incomplete flowers lack one or more of these structures.
6. How Many Types of Flowers are there?
There are over 400,000 known species of flowering plants, with a wide variety of shapes, colors, and sizes. They can be broadly categorized into monocots and dicots, based on the number of cotyledons in their seeds.
7. What is the National Flower of India?
The national flower of India is the Lotus (Nelumbo nucifera). It was adopted as national flower on 26 January 1950. It represents enlightenment and knowledge.