Note on Family- Compositae

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Class: Dicotyledonae

Sub-class: Gamopetalae

Series: Inferae

Order: Asterales

Family: Asteraceae

Distribution

This is the largest family of angiospermae which includes 1100 genera and over 20,000 species. The members are cosmopolitan in distribution and are found in all possible habitats of trophics, sub-trophics, temperate and subalpine regions.

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Vegetative characters

Habit

Annual, biennial or perennial herbs, shrubs (Solidago, Senecio), sometimes trees (Leucomeris), rarely climbers (Senecioscandens). Most of the plants possess milky or watery or resinous and bitter juice which is the characteristic feature of this family.

Root

Branched tap root system, sometimes fibrous also, in some species like Dahlia, Helianthestuberosus etc. The adventitious roots are modified into fasciculated root due to the storage of food materials.

Stem

Aerial, erect or prostrate or a creeping or sometimes climbing with distinct nodes and internodes, branched, herbaceous or woody, cylindrical, solid, rarely fistular, pubescent or glabrous, sometimes branches get modified into thorns (Proustia).

Leaf

Cauline and ramal, sometimes radical(Launaea), exstipulate, petiolate or sessile, alternate or sometimes opposite (Helianthes) or whorled (Eupatorium). Simple or sometimes highly dissected (Artemesia), rarely compound. Sometimes leaves get modified into scales(Odontospermum), spines(Hallophylum), reticulate venation, sometimes parallel venation(Corymbium).

Reproductive characters

Inflorescence

Racemose, head or capitulum consisting of many small flowers developed on the flat or concave or convex receptacle surrounded by an involucre of bracts.

Flower

Flowers being very small are known as florets. Two types of florets are present i.e. ray floret and disc floret. Ray floret(Ligulate) occurs towards the periphery and tubular disc floret towards the centre.

Ray floret

Bracteate or ebracteate, sessile, ligulate, incomplete, unisexual, pistillate, trimerous, sometimes pentamerous, zygomorphic, epigynous.

Calyx

Sepals are modified into thin membranous hair-like structures known as pappus or modified into bristles or scales, persistent, superior.

Corolla

Petals 3 or 5, gamopetalous, ligulate, valvate aestivation, superior.

Androecium; Absent

Gynoecium

Carpels(2), bicarpellary, syncarpous, ovary inferior, unilocular with single ovule in basal placentation. Style single, simple and stigma usually bifid.

Fruit

Cypsela

Floral formula

Br or Ebr% Kpappus C(3)\( \overline{G} \)(2)

Disc floret

Bracteate or ebracteate, sessile, tubular, complete, bisexual, actinomorphic, pentamerous, epigynous.

Calyx

Sepals are modified into thin membranous hair-like structures known as pappus or modified into bristles or scales, persistent, superior.

Corolla

Petals(5), gamopetalous, sometimes swollen near the base of the style, valvate aestivation, superior.

Androecium

Stamens(5), syngenesious, epipetalous, anthers dithecous, basifixed, sometimes adnate, introrse, superior.

Gynoecium

Carpels(2), bicarpellary, syncarpous, ovary inferior, unilocular with single ovule in basal placentation, style single and simple, stigma usually bifid.

Fruit

Cypsela

Floral formula

Br. or Ebr. Kpappus(5) A(5)\( \overline{G} \)(2)

Economic importance

Ornamental plants

  • Helianthus annus (sunflower)
  • Tagetes sps(Marigold
  • Dahlia hybrida (Dahlia)
  • Calendula sps (Pot marigold)

Food plants

  • Carthamus tinctorius (Safflower)
  • Lactuca sativa (Lettuce)

Medicinal plants

  • Artemeria vulgaris (Artemeria)
  • Solidago sps (Golden rod)

  • This is the largest family of Angiospermae which includes 1100 genera and over 20,000 species. 
  • The members are cosmopolitan in distribution and are found in all possible habitats of trophics, sub-trophics, temperate and subalpine regions.
  • Most of the plants possess milky or watery or resinous and bitter juice which is the characteristic feature of this family.
  •  Ray floret(Ligulate) occurs towards the periphery and tubular disc floret towards the centre.
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