Asteraceae : Morphological Diversity of Families|Floral Formula and Floral Diagram | Dicotyledons

Asteraceae : Morphological Diversity of Families|Floral Formula and Floral Diagram | Dicotyledons

 Asteraceae : Morphological Diversity of Families to know about this topic read this full article.

Systematic position

Class- Dicotyledonae

Subclass- Gamopetalae

Order- Asterales

Family- Asteraceae

Distribution :

Asteraceae is the largest family of flowering plants containing at least 1528 genera and 22750 species distributed mainly in temperate and subtropical regions.

Selected Indian genera: Ageratum,  Chrysanthemum, Dahlia, Eclipta, Heliathus, Sonchus,  Tagetes.

Habit:

 Herbs, shrubs or trees (Veronia arborea).

Vegetative Charaters of Asteraceae:

Stem: Herbaceous, Aerial, erect, branched and with milky sap.

Leaves: Simple or compound, spiral or opposite (rarely whorled),

exstipulate.

Floral Characters of Asteraceae

Inflorescence: Capitulum (Head) with distinct involucre cup formed of bracts. The capitulum may be solitary or may be arranged into cymes. The marginal sterile or female  flowers are called ray florets, these are ligulate.

The central bisexual flowers are called Disc florets.

Disc Florets: Actinomorphic, hermaphrodite, tubular  epigynous and bisexual.

Calyx: Calyx in Asteraceae family is represented by a ring of small teeth of numerous hairs or scales, so called pappus (Ageratum conyzoides).

Corolla: 5 petals, gamopetalous and tubular.

Androecium: 5 stamens. Epipetalous, syngenesious.

Gynoecium: Bicarpellary, syncarpous, ovary inferior, unilocular with single anatropous ovule, style is simple, stigma bifid.

Ray Florets:

In ray florets Zygomorphic, Pistillate (female) ,

ligulate and epigynous.

Calyx:  pappus.

Corolla: 5 petals, gamopetalous, strap shaped (ligulate),

valvate aestivation.

Fruit: Cypsela often crowned by persistent pappus.

Seed: Non-endospermic, embryo straight.

flower of Asteraceae

Androecium- Absent

Gynoecium- Bicarpellary and syncarpous, ovary inferior and unilocular with basal placentation. Style mostly bifid.

Floral formula

floral formula of Asteraceae

Ageratum conyzoides

Habit: Annual herb

Root: Tap root, branched

Stem: Aerial, erect, cylindrical, branched, solid, hairy and soft.

Leaf: Ramal and Cauline, simple, petiolate, exstipulate, opposite, ovate, serrate margins, acute and hairy, venation reticulate unicostate.

Inflorescence: The primary aggregation of flowers is a head ( Capitulum) clusterd in a Corymbose inflorescence. The corymb are terminal heads with no distinction into rays and disc florets.

Flower: sessile, Bracteate, ebracteolate, complete, pentamerous, actinomorphic, bisexual and epigynous, flower violet in colour.

Calyx: Sepals 5, but reduced to scaly structure called pappus, aestivation valvate.

Corolla: Petals 5, gamopetalous, tubular, violet in colour, aestivation valvate.

Androecium: Stamens 5 alternate with the petals and epipetalous, filaments short, anthers long syngenecious, basifixed. Bithecous, introse, dehiscing longitudnally.

Gynoecium: Ovary inferior, bicarpellary, syncarpous, unilocular with only one ovule on basal placenta. Style long divided into two arms. Stigmas long, flattened at the tip, glandular papillae present on the stigma.

androecium  and gynoecium of Asteraceae

Fruit: A Cypsela, black in colour. At the tip of the fruit are present 5 scales of the calyx.

Seed: exalbuminous.

Pollination- by large variety of insects. Single visit of insects may pollinate large number of flowers.

To know about Fabaceae (Leguminosae) : Morphological Diversity CLICK HERE

To know about Brassicaceae (Cruciferae)/Mustard Family : Morphological Diversity CLICK HERE 

To know about Ranunculaceae : Morphological Diversity Of Families : Dicotyledons CLICK HERE

to know more about Malvaceae : Morphological Diversity Of Families : Dicotyledons CLICK HERE

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