Whorls of Flowers

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 reproductive parts of flowers and structure. 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). The corolla part of flower 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.

Also Read: Types 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, embryo sac 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.

A flower is the reproductive structure of angiosperm that facilitates sexual reproduction. The 4 main parts of the flower include – sepals, petals, stamens (male parts of the flower), and carpels (female part of the flower). The different parts of the flower have their unique function. The primary function of the flower is reproduction in plants, attracting pollinators for fertilization and producing seeds and fruits.

In this article we will study, parts of a flower and their function.