Introduction

• A Flower is a specialized shoot in which the leaves are modified into floral structures

Structure of a complete flower

Basic Terminologies

• There is the stalk (Pedicel) which supports the flower. Some flowers may be sessile ie. without a stalk.

• The tip of the stalk is enlarged to form a cup-shaped receptacle or thalamus.

• The floral parts are borne on the thalamus in four whorls:

1. First whorl- Sepals (green) –>collectively called as Calyx.
2. Second whorl- Petals (large-brightly coloured) –> collectively called as Corolla.
3. Third whorl- Stamens (Male parts) –> collectively called as Androecium.
4. Fourth whorl- Pistil/carpel (Female part) –> collectively called as Gynoecium.

Stamens is composed of:

• A long tubular structure or stalk like structure: Filament
• A Bilobed Structure at the distal end of the filament: Anther

Pistil is composed of:

• Stigma
• Style
• Ovary

Essential /Non-Essential Parts

• Essential (Reproductive) part- Parts of a flower those are directly concerned with reproduction.

1. STAMENS (male-parts)
2. CARPELS (female-parts)

• Non-essential (Vegetative/accessory) part- Parts that are helping either by protecting the reproductive parts of the flower or make the flower look attractive for pollination.

1. SEPALS
2. PETALS

• In some cases, the sepals and petals look very similar and cannot be differentiated from one another called as Tepals, collectively called as Perianth.

Bracts & Nectaries

• BRACTS:

1. When a flower arises in the axil of a leaf-like structure, this structure is called as Bract.
2. Bracts may be green like ordinary leaves or at times they are coloured.
3. The actual flower in this case is small.
4. E.g.- Bougainvillea

• NECTARIES:

1. Flower produce a sweet fragrant liquid called as Nectar.
2. Groups of nectar secreting cells are called as Nectaries.
3. Nectaries are situated usually at the base of the pistil.
4. The nectar attracts insects for cross pollination. E.g.- Honeybees.
5. Plant in which the nectaries are very prominent- Nasturtium.

Sexuality In Flowers

• A Flower which contains both stamens and carpels is called a bisexual or Hermaphrodite flower.
• E.g.- Hibiscus, rose, lily.
• A flower which has only one of part, either the stamens or the carpels is called an unisexual flower or an imperfect flower.
• E.g.- Palm, Papaya.
• An unisexual flower which contains only the stamens is called as the male or the staminate flower.
• A flower which contains only the carpels is called the femaleor pistillate flower.
• Neuter flower- a flower in which both male and female reproductive organs are lacking.
• E.g.- Ray florets of sunflower (Pistillate but sterile)

General Description Of Floral Parts

• Calyx (Sepals)

1. Usually there are five sepals, some may be free (polysepalous) and some fused (gamosepalous).
2. Epicalyx: In Hibiscus, there may be a second series of sepals called as episepals, collectively called as epicalyx.
3. When the flower falls, the sepals may fall off or persist.
4. Sepals are usually green but in some cases they are brightly colored called as petaloid sepals. E.g.- Gul Mohur (Red).
5. Function of sepals:

❖They protect the young flower bud

❖When green they also perform photosynthesis.

• Corolla (Sepals):

1. Plants with double whorl of corolla. E.g.- Poppy
2. Plants whose whorl of corolla are arranged spirally. E.g.- Water lily.
3. Petals may be free – Polypetalous
4. Petals may be united – Gamopetalous
5. Functions of petals:

❖The colorful and fragrant petals attract insects for pollination.

❖They also protect stamens and pistils.

• Androecium (Stamens):

1. The number of stamens vary from plants to plants.
2. Each stamen consists of:

❖A long tube: Filament

❖A bilobed (2 lobes) structure attached to the filament: Anther

3. Each lobe of anther has two pollen sacs , within the pollen sacs pollen
grains are present.
4. When fully matured the pollen sacs rupture to liberate pollen grains.
5. Androecium can be classified on the basis of their orientation: 

Monadelphous	Diadelphous	Polyadelphous
Stamens are united in one group by their filaments. Only anthers are free.	The filaments are united in two bundles. 9 stamens form a staminal tube while one is free	The filaments are united in several groups.
Eg- China rose	Eg- Pea	Eg- Bombax

• Gynoecium (Carpels/pistils):

Each carpel consists of 3 parts:

Stigma	Style	Ovary
It is the terminal knob-like part, may have a feathery appearance.	It is the tubular slender stalk which connects the stigma to the ovary.	It is the swollen basal portion composed of one or many carpels fused together.
It is covered by a glandular papillae.		The inner cavity of the ovary may be a single chamber or divided into several chambers called as locules.
It serves as the landing platform for pollen during pollination.		Each locule contains an ovule.
		Placenta attaches the ovules to the wall of the ovary.

Difference between
Monoecious & Dioecius

Monoecious plants	Dioecious plants
Male and female flowers grow on the same plant.	Male and female flowers grow on different plants.
E.g- Maize, cucumber, pumpkin etc.	E.g- Palm, papaya etc.

Inflorescence

• Inflorescence is the mode of arrangement of flowers on the axis of a plant.

• Types of Inflorescence:

1. Racemose (Indefinite)
2. Cymose (Definite)

Placentation

• Placentation is the manner in which the ovules are arranged/attached to the wall of the ovary.
• Placenta : It is the tissue that attaches the ovule to the wall of the ovary.
• After fertilization:

1. Ovules turns into seeds.
2. Fruit turns into ovary.