FlowerB.Sc.-II Sem

BY

DR. PRAVIN J. KALE

Assistant Professor

Department of Botany

Narayanrao Kale Smruti Model College Karanja (Gh.)

The Description of Flowers

• A flower is the reproductive unit of anangiosperm plant. There is an enormousvariety of flowers, but all have somecharacteristics in common. The definitivecharacteristic of the angiosperms is theenclosed ovary, which contains and protectsthe developing seeds.

• Floral reproduction is bisexual, and flowershave "male" and "female" parts. The "male"or pollen-bearing part is called the stamen,and is composed of the filament andthe anther. The "female" or seed-bearing partis called the pistil, and is composed ofthe ovary, the stigma, and the style. A flowermay have exclusively male parts, exclusivelyfemale parts, or commonly, both. When thereare separate flower types, both may occur onthe same plant; occasionally a plant may bearonly male or female flowers.

.Actinomorphic(= regular)

Flowers that are radially symmetrical sothat they are able to be bisected intosimilar halves in more than one verticalplane, forming mirror images

Zygomorphic(=irregular)

Flowers that are bilaterally symmetrical so that they are able to be bisected

into similar halves in only one plane, forming mirror images.

Symmetry of flower-Actinomorphic versus Zygomorphic

Pistillode-Sterile gynoecium Staminode-Sterile stamen

• Bract:A leaf-like element below a flower or on an inflorescence. Bracts are typically shaped differently than other leaves on the plant. They are usually green, but occasionally are brightly colored and petal-like.

• A bract is a modified or specialized leaf, especiallyone associated with a reproductive structure suchas a flower, inflorescence axis or cone scale.Bracts are often (but not always) different fromfoliage leaves. They may be smaller, larger, or of adifferent color, shape, or texture. Typically, theyalso look different from the parts of the flower,such as the petals or sepals. The state of havingbracts is referred to as bracteate or bracteolate,and conversely the state of lacking them isreferred to as ebracteate and ebracteolate,without bracts.

• Some bracts are brightly colored and serve the function of attracting pollinators, either together with the perianth or instead of it. Examples of this type of bract include Euphorbia pulcherrima (poinsettia) and Bougainvillea: both of these have large colourful bracts surrounding much smaller, less colourful flowers.

Bracts along a bananaflower stalk surround

the rows of flowers

Euphorbia milii var.vulcanii cyathia bearing a pair of

pinkish cyathophylls.

• Papery (upper) and leafy bracts on hay rattle (Rhinanthus minor). All the "leaves" in this image are bracts.

• Colourful bracts of

Ananas bracteatus.

Bracts, Taraxacum officinale.

• Dogwood species

• Cornus florida inflorescence showing four large white bracts and central flower cluster

• Cornus Florida dogwood with pink bracts surrounding small flower cluster

Flower Definition• Flowers are the reproductive organs of plants. Flower is the modified vegetative shoot and is

meant for sexual reproduction. Flower arises from a modified leaf called bract. It consists of avery short axis on which whorls of different parts of the flower are present.

Parts of a Flower Flowers are diverse in gross appearance

but the basic parts which make up the

flower are basic throughout. Flower is the

specialized and modified shoot. The

following are the recognized parts of the

flower:

Peduncle

Peduncle is the stalk of a flower.

Receptacle

Receptacle is the stem portion, it is found at the base in the center of the

flower. The internodes are short and the number of leaves is small. Hence,

receptacle is not usually a large part of the flower.

Nectaries are often associated with flowers and are found at the receptacle,

nectaries produce sugary nectar which attracts insects.

Sepals

Sepals form the outermost whorl of the floral

structure. They are mostly but not always

green and are leaf-like in appearance. Sepals

are similar to the foliage leaves of the plant.

Sepals are collectively known as the Calyx.

The major function of the calyx is the

protection of flower parts during early

development of the flower or the bud.

Petals

Petals are present above the sepals whorl.

Petals are larger than the sepals, they are

brightly colored, leaf-like, broad and are thin

organs. The petals collectively are known as

the Corolla.

Corolla is the attractive part of the flower.

They provide additional protection and attract

insects to facilitate pollination of the flower.

The leaf-like organs, the sepals and the

petals are together known as the perianth of

the flower. They are similar in appearance.

Calyx

Sepals are collectively known as calyx. It forms

the outermost whorl of a flower. They are

usually green in color and their typical function

is protection for the flower in bud stage and

also supports the petals when in bloom.

Morphologically sepals are modified leaves.

The calyx are described

as polysepalous when all the sepals

are free from each other, example

Brassica., Rosa sinensis

Calyx are known

gamosepalous when the sepals are

united or fused; example - Datura

In plants like sunflower and tridax the

sepals are reduced into hair like structures

called pappus.

The calyx is said to

be caducous when the sepals fall

off as soon as the flower opens.

Example: Argemone.

The calyx is deciduous if the sepals fall off

at the same time as the corolla. Example:

Brassica

The sepals and petals are known

as perianth. When the sepals and petals

are difficult to distinguish they are known

as tepals, example- Aloe and Tulipa.

In plants like brinjal and tomato, the

sepals are persistent as they

remain without falling off and are

found on the fruit.

In hibiscus the whorl of bracteoles is

attached to calyx cup and is known

as epicalyx.

(a) Regular forms:1. Cruciform:Four free clawed petals are arranged in the form of a cross as in the Cruciferae family, e.g., mustard .2. Caryophyllaceous:This is formed by five free clawed petals with limbs at right angles to the claws as in the family Caryophyllaceae, e.g., the pink flower (Dianthus ).3. Rosaceous:There are five sessile (or with very short claws) petals with the limbs spreading outwards. The odd petal is anterior. This is found in the family Rosaceae (e.g., wild rose ) and also in tea (Thea chinensis). Most cultivated roses however show more petals because of reasons explained .(b) Irregular forms:4. Papilionaceous:Here five free petals resemble a butterfly (papilion=butterfly). The posterior superior petal is larger than the others and is termed the vexillum or standard; two anterior inferior ones are usually more or less united forming a boat-shaped struc-

ture and are called the carina or keel.Two lateral petals called alae or wings overlap the carina and are themselves overlapped by the vexillum. This is a characteristic of the subfamily Papilionaceae, e.g., the pea flower.

(b) Irregular forms:7. Ligulate or strap-shaped:Five petals unite to form a short tube at base which splits on one side and becomes flattened like a strap above as seen in many Compositae, e.g., the ray florets of marigold where one can see that the strap is formed by the union of five petals.8. Bilabiate or labiate or two-lipped:This irregular corolla is united in such a way that the limb is divided into an upper posterior part (usually formed by the union of two petal lobes) and an unequal lower anterior part (usually formed by the union of three petal lobes) with the mouth gaping wide open.This is characteristic of the family Labiatae (e.g., Leucas ) and is also seen in some allied families (e.g., Hygrophila and Adhatoda of Aearithaceae).9. Personate or masked:It resembles the bilabiate but the two lips are placed so close together that the mouth is closed. The projection of the lower lip closing the mouth is called the palate. This type of corolla may be seen in snapdragon (Antirrhinum ) or Lindenbergia.

B. Gamopetalous or Sympetalous:(a) Regular forms:1. Tabular:The corolla tube is nearly cylindrical throughout and the limbs are not spreading. The central florets of most Composite are tubular, e.g., sunflower disc florets.2. Campanulate or bell-shaped:Corolla tubes are rounded at base gradually widening upwards like a bell. This may be seen in the family Campanulaceae and in many cucurbits , in Physalis, etc.3. Infundibuliform or funnel-shaped:The corolla resembles an inverted cone like a funnel as seen in Datura or many plants of the family Convolvulaceae like Ipomoea pulchella .4. Hypocrateriform or salver-shaped:The corolla tube is long and narrow with the limb placed at right angles to it as seen’ in Vinca rosea of Apocynaceac.5. Rotate or wheel-shaped:Here the tube is shorter than in hypocrateriform while the limb is at right angles to it as seen-in brinjal (Solarium melongena), Nyctanthes arbor-tristis of Oleaceae , etc.6. Urceolate or urn-shaped:Corolla tube is swollen in the middle tapering towards both base and apex as in Kalanchoe pinnata of Crassulaccae.

ANDROECIUM

Stamens

Stamens are located inside the corolla and

are leaf-like appearance. Stamens are the

male part of the flower and produces pollen.

Stamens consists of a filament and an anther.

Stamens are collectively called androecium.

Anther is the sac located at the tip of the

filament that contains pollen.

Filament is the stalk that connects to and

holds up the anther.

(1) Basifixed-filament ends just at the base of the anther, the latter being firmly fixed on the top of the former. This condition is called basifixed or innate.

2. AdnateIt is adnate when the filament or its continuation, the connective, appears to be attached throughout the whole length of the back of the anther as seen in magnolia and water-lily.

(3) DorsifixedThe attachment is dorsifixed when the filament is firmly fixed to some position on the back of the anther as in passion-flower, Sesbania, etc.

(4) VersatileIn most grasses and in many lilies the attachment is versatile where the filament, is attached merely at a point about the middle of the connective so that the anther can swing on it freely.

Attachment of the Anther to the Filament:

Type Description Examples

1. Adelphous( 3-types) Filaments are fused, anthers free.Fused filaments form staminal tube.

a. Monoadelphous Filaments of all stamens fused to form one bundle

Hibiscus, Cotton, Ladies finger

b. Diadelphous Filaments of all stamens fused to form two bundles

Pea, Bean, Clitoria

c. Polyadelphous More than two bundles of filaments

Citrus, Lemon

2. Syngenesious Anthers fused, filaments free

Sunflower, Tridax

3. Synandrous Both anthers and filaments are fused

Cucumber, Cucurbita, Cucumis

Cohesion of stamens (With same members)

Adhesion of stamens (With different members)

When stamens adhere, to petals they are termed epipetalous

When stamens are free polyandrous

When stamens adhere, to perianth they are termed epiphyllus

When stamens adhere, to gynoecium they are termed gynostegium

On Length and numbers of stamens

Gynoecium

GynoeciumGynoecium (from gyne, meaning woman, and oikos, meaning house) is most

commonly used as a collective term for the parts of a flower that produce ovules

and ultimately develop into the fruit and seeds.

The gynoecium is the innermost whorl of (one or more) pistils in a flower

The gynoecium is often referred to as the "female“ portion of the flower,.

Flowers that bear a gynoecium but no stamens are called pistillate or carpellate.

•Carpels

•Carpels are one or more in number and

are located in the upper center of the

flower. Collectively the carpels are known

as gynoecium. Carpels are made of three

parts: Ovary. Style and Stigma.

•Ovary is the structure present at the base

of the carpel. It is an enlarged narrow

region bearing one or more ovules.

•Style is the slender, neck-like portion of

the carpel the leads to the ovary.

•Stigma is of variety of shapes and sizes.

It present at the tip of the carpel and is

sticky to collect pollen grains.

If a gynoecium has a single carpel, it is called monocarpous.

If a gynoecium has multiple, distinct (free, unfused) carpels, it is apocarpous.

If a gynoecium has multiple carpels "fused" into a single structure, it

is syncarpous.

A syncarpous gynoecium can sometimes appear very much like a monocarpous

gynoecium.

Bicarpellary:When two carpels are present, e.g., Solanaceae.Tricarpellary:When three carpels are present, e.g., Liliaceae.Tetracarpellary:When four carpels are present, e.g., Datura stramonium.Pentacarpellary:When five carpels are present, e.g., Meliaceae.Multicarpellary:When numerous carpels are present, e.g., Malvaceae.Pistillode:A sterile carpel which lacks any ovule, as in Moraceae.

EXAMPLES

Monocarpellary:Gynoecium consisting of a single carpel, e.g., Leguminosae.

Apocarpous:When carpels are free, e.g., Ranunculaceae.

Syncarpous:When carpels are united or fused to form one compound gynoecium, e.g., Solanaceae.

Hypogynous and Superior:When the gynoecium is borne at the top of the thalamus, and the other floral parts, like androecium, petals and sepals arise below the gynoecium, the condition is called hypogynous and the ovary is called superior Perigynous and Semi-inferior:When sepals, petals and androecium are arranged around the carpel, the condition is called perigynous and the ovary is called semi-inferior.Epigynous and Inferior:When the sepals, petals and androecium arise above the gynoecium, the condition is called epigynous and the ovary is called inferior

Perigynous and Semi-inferior:

Hypogynous and Superior:

Epigynous and Inferior:

Locule and Loculi:The ovary is hollow from inside and encloses a chamber called locule (Fig 86), or chambers called loculi.Unilocular:One – chambered ovary, e.g., Stellaria.Bilocular:Two – chambered ovary, e.g., Acanthaceae (Fig. 86).Trilocular:Three – chambered ovary, e.g., Liliaceae (Fig. 86).Multilocular:Many – chambered ovary, e.g., Malvaceae.Replum:False septum, as in Cruciferae.

PlacentationThe ovules are attached on the inner surface of the ovary walls onone or more cushions called placenta. The manner in whichplacenta (placentae) are arranged on the ovary wall is known asplacentation.Types of placentation :1. Marginal : In the monocarpellary (Pea) or each carpel ofmulticarpellary apocarporous (Ranunculus) gynoecium, there issingle placenta which develops along the junction of two fusedmargins.2. Parietal : When the gynoecium is formed by the fusion of twoor more carpels by their adjacent margins, the ovary is unilocularand has two or more longitudinal placenta e.g., Cucurbita,Mustard, Argemone.3. Axile ; In a multicarpellary syncarpous gynoecium the fusingmargins grow inwards to meet in the center of the ovary to forman axis thus making the ovary multichambered (multilocular). Theovules are borne on the central axis e.g., Solanum, China rose.4. Free central : The ovary is unilocular and the ovules areborne on the axis in the center of the ovary e.g., Dianthus.5. Basal : The ovary is unilocular and a single ovule is borne atthe base of ovary e.g., Sunflower.6. Superficial : The gynoecium is multicarpellary syncarpousand large number of ovules are borne on the walls of loculiwithout specific order e.g., Nymphaea (Water lily).

placentation marginal - pea (Pisum, Leguminosae)

axile - okra (Abelmoschus, Malvaceae)

parietal - papaya (Carica, Caricaceae)

Anthophore

The internode between the

calyx and corolla is known

as anthophore,

Androphore

The internode between the

between corolla and

androecium is androphore,

Gynophore

The internode between

androecium and gynoecium

is gynophore.

Gynandrophore

The internode between both

androphore and gynophore

develop to form what is

known as gynandrophore,

Anthophore of Silene saxifraga

Androphore of passion flower

Gynophore of Bauhinia

Gynandrophore of

Cleome gynandra