Floral Formula

It is a symbolic and numerical representation of floral parts in angiosperms. The floral formula is a system used to represent the structure of a flower using specific numbers, letters, and symbols.

It also furnishes information regarding symmetry, sexuality, and interrelationship of floral parts viz., calyx, corolla, androecium and gynoecium. Floral formulas can be used to describe an entire plant family or a specific species.

Figure : On the left of the image, a simplified aerial view of the flower represents the floral diagram. 

A single dark green circle represents the peduncle (Mother axis).No.1

Three darker green, bracket like shapes represent leaves (Epicalyx) No.2

Five light green crescents that form a circle or outermost whorl (Calyx) No.3

There are 5 pink crescent shapes that form a circle (Corolla) No.4

Stigma surrounded by 5 anthers(Androecium). No.5

In the center is a star-like five lobed stigma or inner most (Gynoecium)No.6

Outer to inner sequence of floral part is calyx,corolla,androecium and gynoecium.

1.0What is Floral Formula?

Floral formula is useful tools for remembering characteristics of the various angiosperm families. Their construction requires careful observation of individual flowers and of variation among the flowers of the same or different individuals.

A floral formula consists of following symbols indicating from left to right:

Floral Symmetry, Number of Sepals, Number of Petals, Number of Stamens and Number of Carpels.

Components of floral formula/symbols for different parts of a flower

2.0Position of the ovary in Floral Formula

In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal. 

If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior, e.g., plum, rose, peach. 

In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.

The position of ovary whether, it is superior, half inferior or inferior is shown by placing a horizontal line below in front and above the symbol of gynoecium respectively.

3.0How to Write Floral Formula?

How to construct floral formula? The writing of floral formula one should start from bract and bracteole then symmetry and sex of flower, calyx, corolla, androecium and gynoecium. The number of parts of each organ is indicated in figures (1, 2,3, 4, 5…) after the relevant symbol (K, C, A, G).

If the parts are free, the figure numeral is placed as such but if they are united, the numeral figure is placed inside bracket . 

Adnation of members of different whorls is shown by joining the top of their symbols by a curved line.

The floral formula can be used to describe the flowers of the particular family or the different species of flower. Let us take few examples of the floral formula to study the floral characteristics.

Example 1 :

The floral diagram and floral formula in figure represents the mustard plant (Family: Brassicaceae). 

Flower: Ebracteate bisexual, complete, actinomorphic,  tetramerous 

Calyx: 4 sepals, polysepalous, arranged in two whorls of two each, imbricate aestivation. 

Corolla: 4 petals, polypetalous, cruciform 

Androecium: 6 stamens, polyandrous

Gynoecium: bicarpellary (two carpels), syncarpous.

Floral formula :

Example 2 :

Floral Formula: % K(5) C1+2+(2) A(9)+1 G1 

Flower: bisexual, zygomorphic 

Calyx: sepals five, gamosepalous; valvate/imbricate aestivation 

Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior standard, two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil), vexillary aestivation 

Androecium: ten, diadelphous (9+1) 

Gynoecium: ovary superior, monocarpellary, unilocular with many ovules, style single

Example 3    

Floral Formula:

Flower: bisexual, actinomorphic 

Calyx: sepals five, united, persistent, valvate aestivation 

Corolla: petals five, united; valvate aestivation 

Androecium: stamens five, epipetalous 

Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules. 

4.0Solved Problems

Q.1 The flowers are described as hypogynous, perigynous and epigynous (With Figure ). How?

Ans. In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal.

If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior, e.g., plum, rose, peach. 

In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.

Q.2 Write the symbol for the following given floral characters -

(a) Calyx (b) Actinomorphic flower (c) Bracteate (d) Inferior ovary

Ans. (a) K  (b) ⊕  (c ) Br  (d) ¯¯G

5.0MCQs (Multiple choice questions Important For NEET)

Q.1 Characters explained by floral formula but not floral diagram from following are

A) Placentation  B) Aestivation 

C) Position of ovary D) Number of carpels 

E) Number of locules 

(1) A, B & D only (2) A, C & D only 

(3) C & D only (4) C & E only

Ans. (4) C & E only

Q.2 Without the differentiation of calyx and corolla, the floral organs which are non-essential are called as ___________

(1) Lodicules (2) Pedicel

(3) Thalamus (4) Perianth 

Ans. (4) Perianth 

Q.3 A flower is decided as bisexual flower on the –

(1) Presence of Stamens (2) Presence of Pistils

(3) Presence of both 1 and 2 (4)Presence of either 1 or 2 

Ans. (3) Presence of both 1 and 2

Q.4 Which among the following is incorrect about the symbols used in a floral formula?(1) K is used to represent the calyx of a flower(2) C is used to represent the perianth of a flower(3) Br is used to represent the bracetate of a flower(4) A is used to represent the androecium of a flower

Ans. (4)

Q.5 In a flower a superior ovary is represented by ___________

(1) K (2) A (3) G         (4)  $\bar{G}$

Ans. (3)

Q.6 The floral formula has which of the following symbol to represent zygomorphic symmetry of a flower?

(1) # (2) % (3) K (4) C

Ans. (2) %

Q.7 A floral formula does not tell about

(1) Ovary position (2) Whorls of floral parts

(3) Number of floral parts (4) Placentation and aestivation

Ans. (4) Placentation and aestivation