Parts of a Flower and their Functions

Morphology is a branch of science that deals with the forms and structures of organisms. It is basically studying the size, shape, and structure of plants. The flower is the reproductive unit of angiosperms. It is known for sexual reproduction. Flowers are attractive, colourful and fragrant structures of flowering plants. It is a highly condensed modified reproductive shoot. A typical flower has four different kinds of whorl arranged on the stalk or pedicel, called Thalamus and Receptacle. These are Calyx, Corolla, Androecium and Gynoecium. In some flowers like lily, the calyx and corolla are not distinguishable and are termed perianth. When a flower has both androecium and gynoecium, it is bisexual.  A flower having only stamens or only carpels is unisexual.

Parts of 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. So the flower structure is broadly divided into the following parts:

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. 

Duration of the Calyx 

• Caducous or fugacious is a type of calyx in which some flowers drops off the calyx as soon as the flower opens. Example -poppy, Argemone Mexicana, etc.
• Deciduous is a term used to refer calyx of a flower which falls off along with the petals just after the fertilisation. Example-Mustard, etc.
• The persistent calyx is when it is attached to the ripe fruit. Example- Ocimum, trapa, brinjal, etc.

Function of the Calyx

• Protection of the Flower – calyx performs function as the protection tool of the flower. It saves the flower from external damage.
• Photosynthesis- Further function of calyx is to perform photosynthesis as it is a green leafy part in which food production takes place.
• Defence against Insect-  As described earlier calyx protect the flower from external damage and hence defence against insects.

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.

Function 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.

Types of Anther

Anther is classified into two main types,based on its structure and attachment with the filament.

Based on structure

1. Bilobed– It is the most common type of anther that consist of bilobed structure which can be seen in all mature stamens of the angiosperms.
2. Unilocular- It consist of a single lobe .This condition can be arise due to destruction of one lobe or destruction of longitudinal grooves.
3. Linear- this occurs in the genus Acalypha.
4. Rounded- this appear in the genus Merculiaris.
5. Sagittate- it occur in genus vinca.
6. Reniform- china rose consist of reniform anther

Based on attachment to the filament

1. Adnate- anther present in a continuous manner with filament. for example magnolia and lily.
2. Innate- the filament is attached to the basal region of an anther. it is also known as basifixed anther.
3. Dorsifixed- the filament is attached to the back side of an anther or the dorsal side.
4. Versatile- anther is attached to the middle of the filament.

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.

Conceptual Question

Question1: What is the function of calyx?

Answer 1:

As the calyx is the outermost green protective whorl and its unit is sepal. It helps in the photosynthesis process in which plants make their own food. Furthermore, it helps in the protection of the flower.

Question 2: Define the parts of gynoecium?

Answer:

Gynoecium comes under the essential whorl of a plant. It is known as the female reproductive portion. its parts include stigma, style and ovary. ovary consists of the ovule.

Question 3: What is the function of a flower?

Answer:

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.

Question 4: what is rosaceous corolla?

Answer:

Rosaceous is a type of corolla in which 5 petals of a flower are spread like that of a rose.

Question 5: What is the epipetalous condition?

Answer:

When stamens are attached to the petals, the condition is called Epipetalous condition. For example- brinjal.