Biology

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Construction of Floral Diagram and Floral Formula

A floral formula is a simple way to explain the salient features of a flower. The floral diagram is a representation of the cross section of the flower. It represents floral whorls arranged as viewed from above. Floral diagram shows the number and arrangement of bract, bracteoles and floral parts, fusion, overlapping and placentation. The branch that bears the flower is called mother axis.

The side of the flower facing the mother axis is called posterior side. The side facing the bract is the anterior side. The members of different floral whorls are shown arranged in concentric rings.

Br: Bracteate
Ebr: Ebracteate
Brl: Bracteolate
Ebrl: Ebracteolate
⊕: Actinomorphic
%: Zygomorphic

K: Calyx, K₅ five sepals, aposepalous, K(₅) five sepals synsepalous.
C: Corolla, C₅ five petals, apopetalous, C(₅) five petals sympetalous C(₂₊₃) corolla bilabiate with upper lib two lobes.
A: Androecium A₃ three stamens free, A₂₊₂, Stamens 4, two whorls (didynamous) each whorl two stamens (free)

A₍₉₎₊₁ 
Stamens ten, two bundles (diadelphous) 9 stamens unite to form one bundle, 1 stamen form another bundle.

Epipetalous represented by an arc.

A⁰: Staminode(sterile stamen)
G. Gynoecium or pistil – G₂ – Carpels two, free (apocarpous)
G₍₃₎ – Carpels three, united (syncarpous)
G₀ – Pistillode (sterile carpel)

\(\underline{G}\) – Superior Ovary
G inferior Ovary
G- – Semi-inferior ovary
∞ – Indefinite number of units

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Gynoecium – Definition, Types and its Structure

Gynoecium or pistil is the female reproductive part of the flower. A pistil consists of an expanded basal portion called the ovary, an elongated section called a style and an apical structure that receives pollen called a stigma. Ovary with stipe is called stipitate ovary.

Carpel:
They are components of a gynoecium. Gynoecium is made of one or more carpels. Carpels may be distinct or connate.

Number of Carpel

Fusion of Carpels

It is an important systematic character. Apocarpous gynoecium is generally thought to be ancestral condition in Angiosperms.

Number of Locules

Ovary bears ovules on a specialized tissue called placenta. A septum is a crosswall or partition of ovary. The walls of ovary and septa form a cavity called locule. Like that tetralocular and pentalocular ovaries are present according to the locule numbers four or fie. More than one locule ovaries are called plurilocular.

Extension of the Condensed Internode of the Receptacle

1. Anthophore:
The internodal elongation between calyx and corolla. Example: caryophyllaceae (Silene conoidea)

2. Androphore:
The internodal elongation between the corolla and androecium. Example: Grewia.

3. Gynophore:
The internodal elongation between androecium and gynoecium. Example: Capparis.

4. Gynandrophore or Androgynophore:
The unified internodal elongation between corolla and androecium and androecium and gynoecium. Example: Gynandropsis.

Ovary Position

The position or attachment of ovary relative to the other floral parts. It may be classified into

1. Superior Ovary:
It is the ovary with the sepals, petals and stamens attached at the base of the ovary.

2. Inferior Ovary:
It is the ovary with the sepals, petals and stamens attached at the apex of the ovary.

3. Half-inferior Ovary:
It is the ovary with the sepals, petals and stamens or hypanthium attached near the middle of the ovary.

Perianth/Androecial Position on Thalamus:
It describes placement of the perianth and androecium relative to the ovary and to a hypanthium, if present (Figure 4.25).

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Androecium – Definiton of Androecium and its Various Types

Androecium:
Third whorl of flower is the male reproductive part of the flower. It is composed of stamens (microsporophylls).

Each Stamen consist of 3 parts:

• Filament
• Anther
• Connective

Anther:
Upper swollen part with microsporangia.

Filament:
Stalk of stamen

Connective:
Tissue connecting anther lobes with filament

Anther typically contains two compartments called thecae (singular theca). Each theca consists of two microsporangia. Two microsporangia fused to form a locule. Sterile stamens are called Staminodes. Example: Cassia. Distinct: stamens which do not fuse to one another. Free: stamens which do not fuse with other parts of flower. Apostemonous: flowers with stamens that are free and distinct.

Fusion of Stamens:
The fusion of stamens fusing among themselves or with other parts of flower. They are of two types.

• Connation and
• Adnation

1. Connation:
Refers to the fusion of stamens among themselves. It is of 3 types:-

• Adelphy
• Syngenecious
• Synandrous

Adelphy:
Filaments connate into one or more bundles but anthers are free. It may be the following types.

(i) Monadelphous:
Filaments of stamens connate into a single bundle. Example: Malvaceae (Chinarose, Cotton).

(ii) Diadelphous:
Filaments of stamens connate into two bundles. Example: Fabaceae (pea) and Clitoria.

(iii) Polyadelphous:
Filaments connate into many bundles. Example: Citrus, Bombax

Syngenesious:
Anthers connate, filaments free. Example: Asteraceae.

Synandrous:
Filaments and anthers are completely fused. Example: Coccinea.

2. Adnation:
Refers to the fusion of stamens with other flral parts. Epipetalous: Stamens are adnate to petals. Example: Brinjal, Datura.

a. Episepalous:
Stamens are adnate to sepals. Example: Grevillea (Silver oak)

b. Epitepalous (Epiphyllous):
Stamens are adnate to tepals. Example: Asparagus.

c. Gynostegium:
Connation product of stamens and stigma is called gynostegium. Example: Calotropis and Orchidaceae.

d. Pollinium:
Pollen grains are fused together as a single mass Example: Calotropis

Arrangement of stamens relate to length of stamens:

1. Didynamous:
Four stamens of which two with long fiaments and two with short filaments. Example: Ocimum

2. Tetradynamous:
Six stamens of which four with long filaments and two with short filaments. Example: Brassica.

3. Heterostemonous:
Stamens are of different lengths in the same flower. Example: Cassia.

Anther Types

1. Monothecal:
One lobe with two microsporangia. They are kidney shaped in a cross section. Example: Malvaceae

2. Dithecal:
It is a typical type, having two lobes with four microsporangia. They are butterfly shaped in cross section. Example: Solanaceae.

Anther Attachment

1. Basifixed:
(Innate) Base of anther is attached to the tip of filament. Example: Datura.

2. Dorsifixed:
Apex of filament is attached to the dorsal side of the anther. Example: Hibiscus.

3. Versatile:
Filament is attached to the anther at midpoint. Example: Grasses.

4. Adnate:
Filament is continued from the base to the apex of anther. Example: Nelumbo

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Accessory Organs – Everything You Need to Know

Arrangement of Whorls

The position of perianth (sepals, petals, tepals) parts relative to one another is called perianth arrangement.

1. Cyclic or Whorled:
All the floral parts are arranged in definite whorls. Example: Brassica.

2. Acyclic or Spiral:
The floral parts are arranged in spirals on the elongated fleshy torus. Example: Magnolia.

3. Spirocyclic or Hemicyclic:
Some parts are in whorls and others parts are in spirals. Example: Annona, Polyalthia

Calyx

Calyx protects the flower in bud stage. Outermost whorl of flower is calyx. Unit of calyx is sepal. Normally green in colour.

1. Fusion:

a. Aposepalous (Polysepalous):
The flower with distinct sepals. Example: Brassica, Annona.

b. Synsepalous:
The flower with united or fused sepals. Example: Hibiscus.

2. Duration of Floral Parts:

What is the green part of brinjal fruit? Have you seen similar to this in any other fruits?

a. Caducous or Fugacious Calyx:

Calyx that withers or falls off during the early development stage of flower. Example: Papaver.

b. Deciduous:

Calyx that falls soon after the opening of flower (anthesis) Example: Nelumbo.

c. Persistant:

Calyx that persists and continues to be along with the fruit and forms a cup at the base of the fruit. Example: Brinjal.

d. Accrescent:

Calyx that is persistent, grows along with the fruit and encloses the fruit either completely or partially. Example: Physalis.

3. Shapes of Calyx

Have you noticed the shoe flower’s calyx? It is bell shaped called Campanulate. The fruiting calyx is urn shaped in Withania and it is called urceolate. In Datura calyx is tube like and it is known as tubular. Two lipped calyx is present in Ocimum. Sometimes calyx is coloured and called petaloid. Example: Saraca and Mussanda. In Tridax, calyx is modified into hair like structures are called pappus.

Corolla

Corolla is the most attractive part in majority of the flowers and is usually brightly coloured. Corolla helps to display the flower and attracts the pollinators.

1. Fusion:

a. Apopetalous (Polypetalous):

Petals are distinct. Example: Hibiscus.

b. Sympetalous (Gamopetalous):

Petals are fused. Example: Datura.

Perianth

Can you recall the term homochlamydeous? Undifferentiated calyx and corolla in a flower is called perianth. Each member is called tepal. If the tepals are distinct they are called Apotepalous (Polyphyllous). Example: Allium sativum. Fused tepals are called Syntepalous. (Gamophyllous). Example: Allium cepa.

Aestivation:

Arrangement of sepals and petals in the flower bud is said to be aestivation.

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Flower – Definition of Flower and its Various Types

In a plant, which part would you like the most? Of course, it is a flower, because of its colour and fragrance. The flower is a significant diagnostic feature of angiosperms. It is a modified condensed reproductive shoot. The growth of the flower shoot is determinate.

Whorls of Flower

There are two whorls, accessory and essential. Accessory whorl consists of calyx and corolla and essential whorl comprises of androecium and gynoecium. Flower is said to be Complete when it contains all four whorls. An Incomplete flower is devoid of one or more whorls.

Flower Sex
Flower sex refers to the presence or absence of androecium and gynoecium within a flower.

1. Perfect or Bisexual:
If a flower contains both androecium and gynoecium it is called as a perfect flower.

2. Imperfect or Unisexual:
When the flower contains only one of the essential whorls is called Imperfect flower. It is of two types:

(i) Staminate Flowers:
Flowers with androecium alone.

(ii) Pistillate Flowers:
Flowers with gynoecium alone.

Plant Sex

Plant sex refers to the presence and distribution of flowers with different sexes in an individual plant.

1. Hermaphroditic:
All the flwers of the plant are bisexual.

2. Monoecious:
Both male and female flowers are present in the same plant Example: Coconut.

3. Dioecious:
Male and Female flowers are present on separate plants. Example: Papaya, Palmyra.

4. Polygamous:
The condition in which bisexual and unisexual (staminate/pistillate) flowers occur in a same plant is called polygamous. Example: Musa, Mangifera.

Flower Symmetry

What is the radius of a circle? Cut a paper into round shape, fold it so as to get two equal halves. In how many planes will you get equal halves? In how many planes you can divide a cucumber in two equal halves? A flower is symmetrical when it is divided into equal halves in any plane running through the center. Flower symmetry is an important structural adaptation related to pollination systems.

1. Actinomorphic (or) Radial or Polysymmetric:
The flower shows two mirror images when cut in any plane or radius through the centre. Normally there are more than two planes of symmetry. Example: Hibiscus, Datura.

2. Zygomorphic (Bilateral Symmetry) or Monosymmetric:
The flower can be divided into 2 equal halves in only one plane. Zygomorphic flower can efficiently transfer pollen grains to visiting pollinators. Example: Pisum, Bean.

3. Asymmetric (Amorphic):
Flower lacks any plane of symmetry and cannot be divided into equal halves in any plane. Parts of such flowers are twisted. Example: Canna indica.