Asteraceae: General characters, Distribution, Important plants, Economic importance and Floral diagram
Posted on : 07-08-2018 Posted by : Admin

Systematic classification of asteraceae, dicotyledonae, gamopetalae, inferae, asterales, asteraceae


General Information

Common name: Asteraceae, Compositae

Number of genera: Asteraceae is also known as Compositae. It is one of the largest families of flowering plants. This family includes 900 genera and about 13,000 species. These form more than ten per cent of the total number of species of flowering plants.

Propagation type: Seeds and fruits

Distribution: The members of this family are distributed throughout the world. They inhabit every conceivable situation. In India this family is represented by about 138 genera and 708 species. The members of this family are found chiefly in Himalayas and mountains of southern and western India.

Asteraceae, vegetative characters, tridax procumbens, compositae family

Vegetative characters

Habitat: Members of this family are mostly mesophytes and some xerophytes are also known in this family.

Habit: Mostly annual or perennial herbs, rarely shrubs (Helianthus annus) and trees (Veronia). Occasionally marsh plants (Caesulia) also occur in this family.

Root system: Generally the root system is branched taproot system. Tuberous are present in Dhalia.The roots and stem may contain oil passages.

Stem: Herbaceous or woody, erect, branched.  Helianthus tuberoses produces stem tubers. Many species have milky white sap. Stems are often covered by trichomes.

Leaf: Leaves are simple, alternate or opposite (Helianthus) or whorled (Eupatorium), exstipulate, petiolate, hairy, reticulate venation. They are simple or pinnately or palmately lobed. In Corymbium the leaves are parallel veined. Sometimes leaves are present in basal rosettes as in Taraxacum.

asteraceae, floral characters, L S flower, androecium, T S Ovary, Stamen, Fruit

Floral characters              

Inflorescence: The primary inflorescence is a racemose head or capitulum. It is terminal or axillary in position. In some species several heads aggregate to form compound head or umble or panicle. Each head is subtended by an involucre of green membranous bracts which are protective in function.

The flowers of this inflorescence are called florets. Number of florets in the head varies from few to many. Sometimes only single florets are present as in Echinopus. The flowers are open in acropetal succession. The florets are borne on a flat, concave or convex receptacle. Each floret is subtended by a receptacular bract called palea.

Flower: Flowers are bracteates, sessile, bisexual (sometimes unisexual or neutral), pentamerous, epigynous. The form of flowers may vary in head and the head may be homogamous or heterogamous.

Homogamous: All the florets are alike in structure and function. They are bisexual and either regular (Veronica) or liguate (Cichorium).

Heterogamous: Florets in heterogamous heads are of two types described below,

Disc florets

They are centripetally arranged complete florets. The florets are bracteate, actinomorphic and bisexual, tubular and epigynous. They do not possess any extra-appendage. So, this floret is illinguate

Calyx: Absent or modified into pappus

Corolla: Sepals 5 in number, Gamosepalous, tubular

Androecium: Stamens 2, epipetalous, syngenesious dithecous

Gynoecium: Bicarpellary, Syncarpous, unilocular, one ovule, on basal placentation style single, stigma bifid

Floral diagram, asteraceae, compositae, floral formula

Ray florets

They are peripherally placed incomplete florets. The florets are zygomorphic and unisexual or neutral. This helps in increasing the attraction of the flower. They possess extra appendages called ligule. So, this floret is ligulated.

Calyx: Absent or hairy pappus or scaly persistent

Corolla: Petals 5 in number, polypetalous, ligulate

Androecium: Absent

Gynoecium: Bicarpellary, syncarpous, unilocular, one ovule, the locule, basal placentation, style narrow and stigma branched, ovary inferior

Pollination: The success of this family lies in their adaptation to cross pollination. The plants of Asteraceae are cross pollinated by a variety of insects. Small flowers are made conspicuous by aggregation into heads. The flower heads are made more attractive by ray florets. A single visit of insect may pollinate large number of flowers. The nectar is secreted by a ring shaped disc found the base of the style. The nectar is in corolla tube. The corolla tube is easily accessible to all insects.

Cross pollination is promoted by protandrous condition of the Androecium. The narrow anthers are united to form a hollow cylinder to collect pollen. When the ovary is unripe, the style has two lobes very close to each other. In this condition, it emerges out through the tubular structure formed by the anthers. As it is emerging out, the hairs on the style brush the pollen out of the tube. After emergence, the branches of the style spread out to receive the pollen from another flower. If cross pollination fails, the branches of the style curve down to touches its own pollen and this brings about the self-pollination. In some species of Asteraceae self-pollination is a rule.

Fruit: The fruit is a Cypsela which is dispersed by pappus hairs (Taraxacum). In Xanthium the fruits are dispersed by animals due to presence of hooks.

Seed: Non-endospermic with straight embryo.

Important plants of Asteraceae

Family Asteraceae is also called as Compositae. This family has more than 900 genera and around 13000 species. The members of this family are distributed throughout the world. The following is a list of some important members of family Asteraceae, arranged alphabetically.

  1. Ambrosia artemisiifollia (Rugweed)

  2. Blumea balsamifera

  3. Calendula officinalis

  4. Carthamus tinctorius (Safflower)

  5. Chrysanthemum cinerariaefolium

  6. Chrysanthemum coccineum

  7. Chrysanthemum marchallii

  8. Cichorium intybus (Chicory)

  9. Cynara scolymus (Globe Artichoke)

  10. Helianthus annuus (Sun flower)

  11. Helianthus tuberosus (Jerusalem Artichoke)

  12. Lactuca saitva (Garden letuce)

  13. Lactuca virosa

  14. Spilanthes paniculata

  15. Tagetes minuta (Stinking roger)

  16. Tanacetum vulgare  (Tansy)

  17. Taraxacum officinale (Common dandelion)

  18. Tragopogon porrifolium  (Vegetable oyster)

  19. Tussilago farfara (Coughwort)

Economic Importance of Asteraceae

The family Asteraceae contributes several food, dye, oil and medicine yielding plants. Also this family includes large number of ornamental plants.

  1. Lactuca sativa is the plant widely grown for vegetable. The leaves of this plant are used in salad preparation.
  2. The tubers of the plants Helianthus tuberosus, Cynara scolymus are used as vegetables.
  3. The roots of Tragopogon porrifolium are edible.
  4. The roots of Cichorium intybus are used in blending coffee.
  5. The seeds of Helianthus annus are the source of edible fatty oil. These seeds are also eaten cooked or raw.
  6. The seeds of Carthamus tinctorius are an important oil seed crop in India. These seeds yield edible oil. These seeds are also used in the manufacture of soaps, paints, varnishes, linoleum etc. This oil cake is used as manure in the fields. The seeds are roasted and eaten. This plant yields red colour dye.
  7. Strong aromatic oil is obtained from Tagetes minuta and Tagitus patula. This oil is used as antiseptic, fly repellent and as a modifier in hair lotions. This oil is also used in high grade perfumes.
  8. The flower heads of Spilanthes paniculata are chewed to relieve toothache and infections of throat and gum. It is a popular remedy for stammering in children.
  9. The drug obtained from florets of calendula officinalis is used in the treatment of sprains, bruises and rashes.
  10. Commercial insecticide is obtained from various species of Chrysanthemum like Chrysanthemum coccineum, Chrysanthemum cinerariaefolium and Chrysanthemum marschallii. This insecticide is called as pyrethrum. 
  11. Flowers and leaves of Tamacetum vulgare yield essential oil which is used as liniment for gout, rheumatism and chronic ulcers.
  12. The plant Taraxacum officinale is cultivated to obtain the drug taraxacum from rhizomes and roots. This drug is used as mild laxative, hepatic stimulant and tonic
  13. Blumea camphor is the essential oil obtained from the leaves of Blumea balsamifera. The leaves of this plant are used to cure insomnia.
  14. The leaves of Tussilago farfara are used in the treatment of colds, cough and asthama.
  15. The dried latex from Lactuca virosa known as lactucarium has sedative and hypnotic properties.
  16. The following are the important ornamental plants of this family:
  • Helianthus annuus (Sunflower)
  • Tagetes erecta (African Marigold)
  • Tagetes patula (French Marigold)
  • Dahlia pinnata (Garden Dahlia)
  • Chrysanthemum carinatum (Tricolor chrysanthemum)
  • Chrysanthemum morifolium (Florists chrysanthemum)
  • Chrysanthemum cinerariaefolium (Dalmatian pyrethrum)
  • Cosmos bipinatus
  • Zinnia elegans
  • Zinnia linearis
  • Coreopis grandiflora
  • Aster amellus
  • Aster grandiflorus
  • Gaillardia pulchella
  • Dimorphotheca sinuate
  • Calendula officinalis (Pot marigold)
  • Centurea moschata (Sweet sultan) 

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