Aestivation

The mode of arrangement of sepals and petals in a floral bud is known as aestivation.

There are five types of aestivation:

i) Valvate: the unit of a whorl i.e. sepal or petal contacts with each other by their

margins but does not overlap each other.

ii) Twisted: the sepals or petals are overlapped each other at the margin

iii) Imbricate: Among the five sepals or petals one is inside, one is outside

and remaining is overlapped at the margin.

iv) Quincuncial: Among the five petals or sepals, two are inside, two are outside and

remaining is overlapped at the margin.

v) Vexillary: among the five petals, the posterior or largest one covers the two lateral

and the latter two covers the interior two. This type of aestivation is commonly found

in the member of Fabaceae family.

Placentation

Placenta: A parenchymatous outgrowth-in the inner wall of the ovary to which the ovule or

ovules are attached.

Placentation: The manner in which the placentae are distributed in the cavity of the ovary is

known as placentation

Types of placentation

i) Marginal- The ovary is one chambered and the placenta develops along the

junction of the two margins of the carpel called the ventral suture e.g.

Fabaceae.

ii) Axile-The ovary is two or many chambered- usually as many as the number of

carpels –and the placentae bearing the ovules develop from central axis e.g.

lemon, orange, china rose, lady’s finger, tomato, potato etc.

iii) Parietal- the ovary is one chambered and the placentae bearing the ovules

develop on the inner wall of the ovary e.g. papaya

iv) Central- The septa or portion walls in the

young ovary soon break down so that ovary becomes one chambred and

placenta bearing the ovules develops from the central axis e.g. Dianthus

v) Free central- The placenta arises from the base of the ovary, projects far into

its cavity as a swollen central axis and bears the ovule all over its surface e.g.

Primula

vi) Basal- In basal placentation, the ovary is one chambered and the placenta

develops directly on the thalamus, bearing the single ovule at the base of the

ovary e.g. rice.

vii) Superficial- the ovary is multichamber, the carpels being numerous, as in

axile placentation. But the placentae developed all round the inner surface of

the partition walls as in water lily.

Androecium

The androcium composed of male parts of flower which is essential whorl for sexual

reproduction. It is composed of stamens and the male flower is termed as staminate flower. Each

stamen is composed of three parts viz. anther connective and filament.

Didynamous

When the stamens are unequal i.e. two are longer and two are shorter.

Tetradynamous

When four stamens are longer and two stamens are shorter e.g. mustard

Monadelphous

The filaments of all the stamens are united to form a tube like structure but the anthers are remaining free e.g. cotton, okra, China rose etc.

Diadelphous

The filaments of all the stamens are united into two bundles e.g. pea, soybean etc.

Polyadelphous

The filaments of all the stamens are united into many bundles and anthers are remaining free e.g. citrus.

Synandrous

The stamens of the androecium are united throughout the whole body i.e. anther and filaments are united e.g. member of Cucurbitaceae family.

Syngenesious

The anthers of stamens are fused and united but the filaments remain free e.g. sunflower, pumkin etc.

Adnate

When the filament is attached throughout the whole length of the anther i.e. from the base to the top e.g. Nicotiana, Magnolia etc.

Basifexed

When the filament is fixed to the base of the anther e.g. Brassica

Dorsifixed

When the filament of stamen is fixed with the dorsal site of the stamen e.g. Sesbania, Annona etc.

Versatile

When the filament is attached with the anther in a single point forming the anther as pendulous e.g. rice.

Gynoecium

It is the female reproductive part of flower and essential whorl of flower for reproductive process. It is composed of pistil or carpel.

Pistil

It is the unit of gynoecium having three parts viz. stigma, style and ovary. It is also termed as megasporophyll.

Hypogynous

Ovary is situated above the thallamus but other whorl remains at the base of thalamus. It is called as superior ovary.

Floral formula

Floral formula means symbol, number or alphabet for expressing the structure and information of flower. It can represent or express the particular structure of a species or generalize the structure of taxa.

Floral diagram

It is a graphic representation of flower structure. It shows the number of floral organs, their arrangement and fusion. Floral diagram is useful for identification of plant and help in understanding the evolution of plant.

Symbols Used in Floral Formulae

Parameter Symbol

Bracteate Br

Ebracteate Ebr

Bracteolate Brl

Ebracteolate Ebrl

Actinomorphic

Zygomorphic %

Bisexual

Male flower

Female flower ♀Epicalyx EpK

Calyx K

Corolla C

Androecium A

Gynoecium G

Ovary superior G

Ovary inferior G

Many ∞