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Asteraceae

This document provides information about the Asteraceae family of flowering plants. It discusses the classification, distribution, morphological characteristics, types of flowers (disc and ray florets), and some economically important species of the family. Key points include that Asteraceae is one of the largest families, comprising around 950 genera and 20,000 species worldwide. It describes the distinguishing features of the family such as the composite flower head (capitulum) made up of disc and ray florets. Common genera mentioned are Helianthus, Eclipta, Tridax, Tagetes and Calendula.

Science◦
ASTERACEAE (compositae) G SELVAM I.M.SC.BOTANY BHARTHIDASAN UNIVERSITY, TRICHY TAMILNADU
CLASSIFICATION SYSTEMATIC POSITION Class - Dicotyledons Sub-class - Gamopetalae Series - Inferae Order - Asterales Family - Asteraceae
DISTRIBUTION  The family Asteraceae includes about 950 genera with probably 20,ooo species.  The family comparises about 10% of the total number of flowering plants.  In india family is represented by 697 species .  They can live in all types of localities such as deserts , arctic regions and aquatic habitats
Vegetative Characters Habitat : The plants are usually herbaceous annuals or shrubs. The plants contain a milky or watery or resinous sap. Outer surface of these plants is covered with different types of hairs. ROOT : The roots constitute a branched , tap-root system. STEM : The stem is herbaceous or woody and erect. It is tuberous in Helianthus tuberosus and leaf-like in Baccharis.
LEAVES : The leaves are usually alternate , simple , petiolate and extipulate. In some species leaves are opposite (eg.Helianthus) or whorld (eg.Eupatorium). Sometimes , The leaves may be pinnately or palmately lobed. leaf Surface is covered with hairs. Leaf margin may be entire or Serrate.
FLORAL CHARACTERS INFLORESCENCE : The inflorescence is a racemose or capitulum. A capitilum consists of disc florets in the centre surrounded by ray florets and an involucre. The florets are arranged in centripetal manner. The extended base of the capitulum is called a receptacle. FLOWER : The flower are bisexual or unisexual or polygamous, rarely neuter. They usually pentamerous , bracteates, sessile and epigynous. There are two types of flowers, namely Disc florets and Ray florets .
TWO TYPES OF FLOWERS
TWO TYPES OF FLOWER DISC FLORET RAY FLORET
DISC FLORET : The disc floret occupy the centre of the capitulum. They are bracteates, sessile , bisexual, regular, actinomorphic and epigynous. CALYX : The calyx is usually represented by a pappus. The pappus is considered to be a reduced and highly modified calyx. In some cases, the calyx is represented by spines
COROLLA : The corolla is tubular or discoid. It consists of 5 united petals (Gamopetalous). Aestivation is valvate. The corolla tube is swollen near the base of the style. ANDROECIUM : The Antroecium consists of 5 epipetalous stamens. The stamens are alternate to petals. The filaments remain free, but anthers are united into a tube around the style. This is called Syngenesious condition. The anthers are dithecous, introse and dehiscing by longitudinal slits. GYNOECIUM : The gynoecium is bicarpellary and syncarpous. Ovary is inferior and unilocular. There is a single anatropous ovule in the locule on basal placentation. The style is slender and branched. There are two stigmas with various forms.
FRUIT : The fruit is a cypsela with pappus. SEED : The seed is dicotyledonous and exalbuminous. RAY FLORET : Ray floret occupy the periphery of capitulum. They are bracteates, sessile, irregular, zygomorphic, ligulate and epigynous. CALYX : The calyx is pappus-like or absent.
COROLLA : The corolla is ligulate (strap-shaped), eg. Bilabiate (the upper lip is 3-lobed and lower lip is 2- lobed. It consists of 5 fused petals (Gamopetalous). Aestivation is valvate. ANDROECIUM : In homogamous heads, the ray flower are bisexual so they have 5 syngenesious stamens.In heterogamous heads, ray florets are usually pistillate or neuter, so stamens are altogether absent.
GYNOECIUM : Bicarpellary, syncarpous, inferior ovary with a single locule as in disc florets ovule is one and placentation is basal. Style is bilobed and stigma is variable. FRUIT : Cypsela SEED: Dicotyledonous and exalbuminous.
COMMON PLANTS Helianthus annuus(Suryakanthi) Eclipta prostrata(karisilanganni) Tridax procumbens(Vettukkaaya-thalai)
Tagetes erecta(sevvannthi) Calendula officinalis(Thulukka Saamanthi)
Tridax procumbens
CLASSIFICATION SYSTEMATIC POSITION CLASS - Dicotyledone Sub-class - Gamopetalae Series - Inferae Order - Asterales Family - Asteraceae Genus - Tridax Species - procumbens
Tridax procumbens HABITAT : Tropical and sub-tropical regions, perennial herb. STEM : Cylindrical, branched, erect. LEAF : Simple, ovate, serrate margin, Reticulate ,opposite decussate , Aromatic. INFLORESCENCE : Head or capitulum
RAY FLORET : Bracteate, zycomorphic, sessial,unisexual, Peripharal. Calyx : pappus like structure. COROLLA : 3 or 4 valvate Aestivation Gamopetalous, Androecium and Gynoecium absent.
DISC FLORET : Bracteate, Actinomorphic, bisexual , Inferior ovary. CALYX : pappus like structure. COROLLA : 5 Gamopetalous valvate Aestivation. ANDROECIUM : Syngenesious stamens. GYNOECIUM : Bicarpellary , syncarpous, unilocular, basal Placentation, style, slender and branchd, inferior ovary. FRUIT : Cypsela
ECONOMIC IMPORTANCE 1.OIL : Many plants gives oil seeds to extract oils. The oil is used for cooking, burning, soap- making, varnish preparations and as lubricant. Examples – Helianthus annuus (Suryakanthi) – Seed Carthamus tinctorius (Sendurakam) – Flower Guizotia abyssinica (Payellu) – Seed 2.DYES : Some plants yield dyes for colouring different materials. Flower heads of Carthamus tinctorius gives a red dye called safflower. Flower heads of Tagetes erecta (Tulukka-samandi) gives a yellow-dye for colouring cotten
3.FOOD : Leaves of Cichorium intybus (kasini keerai) are used in salads. Root powder of those plants is a substitute for coffee or often mixed with coffee. Leaves Lactuca sativa (Lattuce keerai) is used in salads. 4.MEDICINES : Whole plant extract of Artemisia absinthium (machipattri) is given for fever and inflammation of liver. Artemisia vulgaris (makkippu) is used for round worms, fever, asthma and nervous disorders.
5.ORNAMENTAL PLANTS : Tagetes erecta(sevvanthi) Helianthus annuus(Suryakanthi)
Calendula officinalis(Thulukka saamanthi) Parthenium hysterophorus(mookuthi poo)
Asteraceae