Structure of Flower

A complete flower typically has four verticils or whorls. They are as follows –

1. Calyx – The members that make up this whorl are called sepals. Sepals are green leaf-like structures that protect a flower in its early bud stage. Also, it is the outermost whorl of a flower.
2. Corolla – The members that make up this whorl are called petals. These structures are brightly coloured and aid in pollination by attracting insects. Also, they can be seen in different shapes like tubular, wheel-shaped, funnel-shaped or bell-shaped. The corolla and calyx together make up a non-reproductive structure called the perianth.
3. Androecium – They are the male reproductive structures composed of stamens. Each stamen consists of a filament or stalk and an anther. Each anther has pollen sacs that aid in the production of pollen grains.
4. Gynoecium – They are female reproductive structures composed of carpels. A carpel is composed of 3 parts namely ovary, style and stigma

Androecium: 

It is a male reproductive part. It consists of stamens. Each stamen is made up of filament and anthers.

• The stamens may either be free (polyandrous) or remain fused together. Epipetalous- stamens are attached to petals.

The cohesion of stamens fused conditions are as follows.

• Monadelphous: Stamens are united into a single group by union of filaments. The anthers remain free.

• Diadelphous: Stamens are united, and arranged in two bundle s.  (e.g. Pisum)

• Polyadelphous: Stamens are united and grouped onto several bundles. (e.g. Citrus)

• Synandrous: Stamens are united their whole length. Both filaments and anthers will be fused. (e.g. Cucurbita)

• Syngenesious: Stamens are united by the joining of anthers. The filaments remain free. (e.g. Tridax)

The stamens can also be found fused with other whorls. This condition is called adhesion. It may be of different types.

1. Epipetalous: Stamens are found attached (wholly or partially) to the corolla, by means of their filaments. Anthers would be free. (e.g. Ixora)

2. Epiphyllous: When stamens are found attached to the perianth of a flower, it is called epiphyllous condition. (e.g. Gloriosa)

3. Gyandrous: Stamens are attached to the carpel (either by whole length, or by the anthers.  (e.g. Calotropis)

Gynoecium :

The gynoecium of a flower is the female reproductive structure that is most essential for sexual reproduction. The gynoecium has ovaries that produce ovules which eventually develop into seeds and fruit.  Carpel is the main component of gynoecium that consists of ovary, style and stigma.

1. Stigma is a sticky portion at the distal end of a tubular structure called style. It is the primary receptive site where the pollen grains are captured.
2. Style is the major structure that aids in the process of fertilization. The pollen tube reaches the ovary via this tubular style.
3. Ovary is located at the swollen base of the carpel. Style is the elongated tube that links the ovary and the stigma. The ovary produces ovules which are present within chambers known as locules. Based on the number of locules, the ovary can also be classified as multilocular, unilocular, bilocular, etc.
4. pistil : Stigma, ovary and style are together termed as the pistil. A pistil is considered to be a collection of one or more carpels.

Placentation:

It is defined as the arrangement and attachment of ovules within the plant’s ovary.

The part of the ovary where ovules are attached is the placenta.

Types of placentation:

• Axile placentation: When the placenta is placed axially as in a lemon, then such type of placentation is termed axile placentation.

• Marginal placentation: When the placenta forms a ridge along the ventral suture as in pea, then this is known as marginal placentation.

• Free central placentation: When the ovules are born on the central axis, it is called free central as in primrose and Dianthus.

• Basal placentation: In this type of placentation, a single ovule is attached to the placenta and placed at the base of the ovary. Eg. Marigold.

Parietal placentation: In this type of placentation, the ovules develop on the inner wall or periphery of the ovary. Eg. Sunflower, kiwi, cucumber, cantaloupe.

Superficial: The placenta is formed all around the inner surface of the ovary including the septa.

1. Marginal- e.g. pea
2. Axile- e.g. lemon, china rose
3. Parietal- e.g. Argemone, mustard
4. Free central- e.g. Primrose, Dianthus
5. Basal- e.g. marigold, sunflower

The Flower

A flower has four whorls; calyx, corolla, androecium and gynoecium. These are attached to the swollen terminal of pedicel called the thalamus

Flower symmetry:

1. Actinomorphic- radially symmetrical flowers, e.g. chilli, datura, mustard
   1. Zygomorphic- when a flower can be divided into two equal parts in only one vertical plane, e.g. Cassia, pea, etc.

Flowers can be trimerous, tetramerous or pentamerous depending on the multiple of floral appendages present 3, 4 or 5

Types of flowers depending on the presence or absence of bracts (reduced leaf present at the base of pedicel); Bracteate or Ebracteate

Types of flowers based on the position of the ovary:

1. Hypogynous- gynoecium occupies the highest place, above all the other parts. The ovary is known as superior. The sepals, petals and stamens arise from below the ovary.This is the commonest type of ovary. The flower is technically Hypogynous where hypo means flower parts start ‘below’ the ovary. e.g. brinjal, china rose, mustard

• Perigynous- gynoecium is present at the same level as the rest of the parts of a flower. The ovary is known as half inferior, The flower parts arise from the rim of a hypanthium – a cup shaped extension of the base which encloses the ovary. Imagine the hypanthium to be a flat ring and you can see that the flower parts actually arise from below the ovary. The flower is technically Perigynous where peri means ‘around’.  e.g. peach, plum, rose

• Epigynous- thalamus encloses the ovary completely and other parts are present above it. The ovary is known as inferior.  Inferior ovary. The sepals, corolla tube and stamens (filaments plus anthers) arise from above the ovary. The flower is technically Epigynous where epi means ‘above’. e.g. ray florets of a sunflower, guava, cucumber

Aestivation:

The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation.

The main types of aestivations are valvate, twisted, imbricate and vexillary.

Valvate:

When sepals or petals in a whorl just touch one another at the margin, without overlapping, as in Calotropis, it is said to be valvate.

Twisted:

If one margin of the appendage overlaps that of the next one and so on as in china rose, lady’s finger and cotton, it is called twisted.

Imbricate:

If the margins of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur, the aestivation is called imbricate.

Vexillary:

In pea and bean flowers, there are five petals, the largest (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel); this type of aestivation is known as vexillary or papilionaceous.

Families of flowering plants:

Main Difference between Fabaceae, Solanaceae, and Liliaceae

1. Fabaceae is a legume family, Solanaceae is a potato family, and Liliaceae is the lily family.
2. Fabaceae contains peas, chickpeas, and soybean, Solanaceae contain potatoes, tomatoes, and bell pepper, while Liliaceae contain onion, lily, and tulip.
3. Fabaceae is perennials or annuals, Solanaceae is annuals or biennials, while Liliaceae is perennials.
4. Fabaceae is monocarpellary; Solanaceae is bicarpellary, while Liliaceae is tricarpellary.
5. Fabaceae contain pods, while Solanaceae and Liliaceae contain berries or capsules.

Refer Flower formula library notes for more information

Fabaceae	Solanaceae	Liliaceae
It is a large family of trees, shrubs, vines, and herbs.	It is a nightshade or potato family of flowering plants	These are monocotyledonous, perennial, and herbaceous plants.
Legume family	Potato family	Lily family
Dicot	Dicot	Monocot
Peas, chickpeas, and soybean	Potato, tomato, and bell pepper.	Onion, lily, and tulip
Exhibits marginal placentation.	Exhibits axial placentation.	Exhibits axial placentation.
Perennial or annuals	Perennials, biennials, and annuals.	Perennials
Trees, shrubs, vines, and herbs	Herbs, shrubs, small trees	Herbs and shrubs
Monocarpellary	Bicarpellary	Tricarpellary
Contain pods	Contain berry or capsule	Contain berry or capsule
Fix atmospheric nitrogen to improve soil fertility	Contain plant varieties with agricultural importance	Contain decorative and ornamental plants.

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