Table of Contents:

[What Is Floral Formula?](#What Is Floral Formula?)

[Introduction To Floral Formulae](#Introduction To Floral Formulae)

Construction of Floral Formulae

Floral Symbols

[Writing Floral Formula](#Writing Floral Formula)

Frequently Asked Questions

What is Floral Formula?

“The relative position and number of floral parts in relation to the mother axis or inflorescence axis can be expressed numerically.”

Floral formulae are both symbolic and numerical representations of different components of a flower. They provide information about the type and quantity of organs, the type of symmetry, the level of ovary, the presence of fusions, and the connections between the different floral parts, such as the corolla, calyx, androecium, and gynoecium.

Floral formulae provide information about the number and arrangement of organs in a flower, but lack the details of the organ positions. There is a difference between American and European traditions in how floral formulae are expressed, yet they both convey the same information. Floral formulae can be used to describe an entire family of plants, or just a single species.

Introduction To Floral Formulae

Flowers are determinate structures with a typically defined number of organs, bearing pistillate and staminate parts. Organs are set in four series – petals, sepals, stamens and carpels.

Floral formulae are a system to represent a flower’s structure using specific numbers, letters, and symbols, making it a simple way to present salient features of a flower. This system portrays the number of parts, floral symmetry, connotation and adnation, ovary position and insertion. These formulae are helpful for remembering the characteristics of different angiosperm families. It mainly consists of 5 symbols which indicate:

Number of Sepals

Number of Petals

Floral Symmetry

Number of Carpels

Number of Stamens

Position of the Ovaries

Flowers can be described as hypogynous, epigynous, and perigynous based on the position of the corolla, calyx, and androecium relative to the ovary on the thalamus.

The gynoecium in the hypogynous flower occupies the highest position, other parts are located below it. Here the ovary is said to be superior. Such positioning of the ovary can be observed in brinjal, china rose and mustard flowers.

The margin of the thalamus in epigynous flowers shoots upwards, completely surrounding the ovary and connecting it to the other floral parts, thus appearing to be located above the ovary. This is why it is referred to as an inferior position, as seen in the ray florets of sunflower, cucumber, and guava.

In perigynous flowers, the gynoecium is located in the center, with the other floral parts located around the rim of the thalamus at the same level. The ovaries in these flowers are partially inferior, as seen in flowers such as peach, rose, and plum.

Check Out: Difference between Androecium and Gynoecium

Construction of Floral Formulae

Floral whorls are represented in concentric circles, with the outermost circle representing sepals, the second circle representing petals, the third circle representing stamens, and the innermost circle representing carpels.

Calyx is represented by a circle of arcs with triangular tips facing outward. Petals are depicted as arcs with smooth edges, alternating with sepals. If the sepals/petals are free, then the arcs are free; otherwise, the edges of the arcs are connected by lines. Aestivation is indicated by overlapping the edges of the arcs.

The stamens of dithecous anthers have a four-lobed structure, while those of monothecous anthers have a uniform shape and alternate with petals.

The center of the gynoecium is represented by a transverse section of the ovary.

A bract is drawn at the base and bracteoles towards the sides

The Mother Axis is represented at the top of the floral diagram as a small circle with a dot.

If whorls are united, the number assigned after the symbol would be shown in brackets to indicate the number of parts in that specific whole.

The presence of more than one whorl of an organ is indicated by the representative parts. The androecium of a flower having 3 whorls of five stamens each is represented as A5+5+5.

An arrow is formed when two symbols are joined together, beginning at the top of one symbol and ending at the top of the other symbol for the joined symbols.

If the number of organs in a whorl is 0 or fewer than 10, then the symbol will be followed by a 0 (zero); if the number of organs in a whorl is more than 10, then the symbol will be followed by ∞ (infinity).

A line placed under the number of carpels indicates the hypogynous condition. Epigynous condition is indicated by a line placed over the number of carpels.

Learn About: Morphology of Flowering Plants

Floral Symbols

Floral Formulae are used to describe a flower using certain signs and symbols to represent different parts of a flower. Some of the symbols used are:

| Br | Bracteate condition |

| Brl | Bracteolate |

| Epik | Epicalyx |

| Ebrl | Ebrachteolate |

| 0 (zero) | Absence of a particular whorl |

| ∞ | Indefinite number of floral parts in a whorl |

| ⊕ | Actinomorphic Condition |

| % | Zygomorphic Condition |

| C | Corolla (petals) |

| P | Perianth (Tepals) |

| A | Androecium (stamens) |

| G | Gynoecium (Carpels) |

| 🏳️‍⚧️ | Bisexual Flower |

| ⚦ | Unisexual, Staminate Flower |

| 🚺 | Unisexual, pistillate flower |

| K5 | Five sepals, aposepalous |

| K(5) | Five petals gamopetalous |

| C5 | Five petals, apopetalous |

| C(5) | Five petals, gamopetalous |

| | Epiphyllous stamens |

| | Epipetalous stamens |

| A3 | Three stamens free |

| A2+2 | Stamens: 4, 2 whorls |

| A10+1 | Stamens 10, diadelphous – 9 stamens unite to form one bundle and 1 other stamen |

| A0 | Sterile Stamen (Staminode) |

| G0 | Pistillode (Sterile Carpel) |

| G | Semi-inferior Ovary |

| | Inferior ovary |

| | Superior ovary |

The number of floral parts are indicated along with symbols at the base of a floral diagram, and their union is shown by a bracket.

Writing Floral Formula

Start by writing the formula with bract and bracteole, followed by the symmetry and sexuality of the flowers. Then, specify the floral parts – calyx (K), corolla (C), androecium (A) and gynoecium (G). To designate the numbers of parts of each structure, figures such as (1, 2, 3, 4, 5) are used after the corresponding symbols.

If the parts of the flower are fused, the numeral value is placed in brackets; however, if the parts are free, the value is placed as it is. For a bilabiate structure, the number of parts is split into two values, corresponding to the parts in the upper and lower lip.

Joining the top of symbols of different whorls by an arc or curved line indicates the adnation of members. A vertical line between symbols of two floral cycles indicates a break in the alternation of parts of any two successive floral cycles. Whereas placing a horizontal line in front or above the symbol of gynoecium represents the position of the ovary if it is half-inferior, superior, or inferior.

Frequently Asked Questions

What is Androecium and Gynoecium?

Androecium is the male reproductive organ in a flower, while Gynoecium is the female reproductive organ in a flower.

The Androecium produces pollen grains containing male gametes, while the Gynoecium produces ovules with female gametes. The Androecium is composed of anthers and filaments and the Gynoecium is composed of style, stigma and ovary. Both are referred to as reproductive whorls of a flower.

Sepals and Petals are parts of a flower that are typically located at the base of the flower. Sepals are usually green and form a protective layer around the flower bud. Petals are the colorful, attractive parts of the flower that attract pollinators.

Petals are a type of modified leaf that is brightly colored. A collection of petals is referred to as a corolla. The petals are accompanied by another leaf modification called the sepals. A collection of sepals is termed as a calyx.