A typical flower and its parts - Online Science Notes

Flowering plants are kept in the group phanerogams.
They are also known as spermatophytes as they produce seeds.
In higher angiosperms, the flowers are produced for the sexual reproduction. Hence, it is the reproductive part of the plant.
A complete flower consists of mainly four whorls or parts; calyx, corolla, androecium and gynoecium and may consist of the nectar glands.
A thalamus is the suppressed swollen end of the floral axis on which the floral leaves are borne
A flower may be bisexual or unisexual.
Bisexual flower: Both male (androecium) and female (gynoecium) parts are present in the same flower. E.g. mustard, Hibiscus, Datura, pea etc.
Unisexual flower: Only one sex is present in the flower. E.g. cucumber. Such flower is said to be incomplete.
A flower having only male (androecium) is staminate, g. pumpkin, papaya etc. and with only female (gynoecium) is called a pistillate, e.g. pumpkin, mulberry etc.
Monoecious: Male and female flowers are borne on the same plant. E.g. maize, Colocasia
Dioecious: Male and female plants are separate. E.g. papaya, mulberry etc.
Polygamous: When unisexual, bisexual or neuter flowers are present on the same plant. E.g mango, Polygonium
Achlamydous: The flowers are without sepals or petals.
Cyclic flower: Floral parts are present in a circle. E .g. mustard, Malvaceae etc.
Acyclic or spiral flower: Floral parts are arranged spirally. E.g. Magnoliaceae
Actinomorphic: A cyclic flower that can be divided into two equal vertical halves or mirror image by any vertical plane (anterio-posterior).
Zygomorphic: Flower is radially asymmetrical.

Sepals or calyx:

It is the outermost whorl of the flower.
It may be free (polysepalous) or fused (gamosepalous).
They protect the flower in the bud stage.
The sepals having color other than green are called petaloid.
Sepals may be caducous (falling down immediately after opening of flower, e.g. poppy), deciduous (falling down at the time of withering of flower) or persistent (sepals persisting in the fruit).
Modified sepals like in case of Compositae are called pappus or scale.

Petals or corolla:

The colorful and attractive part of the flower is petal and collectively called corolla.
They attract the insects and birds and help in pollination.
They lie inner to the sepals.
The arrangement of sepals or petals with relation to one another in a flower is called aestivation.

Androecium:

The unit structure of androecium is a stamen.
A stamen consists of three main parts; anther, connective and filament.
Stamens are usually bilobed (bithecous) and tetrasporangiate.
Anthers with single lobe (monothecous) and bisporangiate condition are found in members of Malvaceae.
Sterile and undeveloped stamens are called staminodes. E.g. Caesalpiniaceae family.
Stamens shorter than the flower are termed as inserted while those protruding outside the flower are called exserted.

Attachment of anther to the filament:

Adnate: The filament or the connective is attached to the whole length at the back of the anther. E.g. water lily
Basifixed: The filament is attached to the base of the anther. E.g. mustard
Dorsifixed: The filament is attached to the dorsal surface of the anther. E.g. in Caesalpiniaceae
Versatile: The filament is attached to the middle of the connective so that anther lobes can swing on it freely. E.g. most of the grasses

**Types of attachment of anther and filament**

Adhesion of stamen (stamens fused with other floral parts):

Stamens are termed as epipetalous, if fused with the petals (in solanaceae, malvacaeae and compositae).
They are called epiphyllous or epitepalous if fused with the tepals (liliaceae).
Fusion of stamens with pistil is called gynandrousg. Calotropis.

Cohesion of stamen (fusion of stamens among themselves):

Adelphous: The stamens are fused only by their filaments.
Monoadelphous: The filaments are fused together and may form a single group. E.g. members of malvacaeae.
Diadelphous: The filaments fuse together forming two groups. E.g. pea
Polyadelphous: Stamens are found in many groups e.g. Ricinus, Bombax
Syngenacious: The anthers are fused but the filaments are free. E.g. sunflower.
Synandrous: Anthers and filaments (the entire stamen) both fused together. E.g. Cucurbita

Length of the stamen:

Didynamous: 4 stamens; two short and two long. e.g. Ocimum
Tetradynamous: 6 stamens; 2 outer short and 4 inner long. e.g. mustard
Heterostemony: Stamens are of different length. E.g. Cassia

Gynoecium:

The gynoecium or pistil is composed of one or more carpels..
Monocarpellary: A single carpel forming a pistil.
Bicarpellary and polycarpellary: Pistil composed of two or more carpels.
In a polycarpellary pistil, carpels may be free (apocarpous) as in Rannunculaceae or wholly or partially united (syncarpous) as in mustard and malvaceae.
A sterile pistil is a pistillode.
A carpel consists of 3 parts; stigma, style and ovary.
Style connects the ovary with the stigma and stigma is usually at the tip of the style.
Styles are generally terminal (arising from the top of the ovary), lateral (arising from the side of the ovary) in case of Gramineae, gynobasic (arising from the mid-basal part of the o vary) as in Salvia and ocimum.

Ovary as one or more chambers or locules in which ovules are located.
Ovary may be unilocular (with single chamber like in pea), bilocular (with two chambers like in mustard), trilocular (with three chambers like in Asparagus), tetralocular (with four chambers like in Ocimum), pentalocular (with five chambers like in China rose) and multilocular (with more than five chambers like in Lady’s finger).