Solanaceae – Datura metal and Economic importance

SOLANACEAE – the potato family

Systematic position
Class: Dicotyledonae
Sub-class: Gamopetalae
Series: Bicarpellatae
Order: Polemoniales
Family: Solanaceae

General Characters Solanaceae

Distribution

Solanaceae includes about 90 genera and more than 2,800 species. The plants are widely distributed in tropical and subtropical regions.

In India, this family is represented by 21 genera and 70 species.

Habit

Mostly annual herbs (eg. Solanum melongena), a few shrubs eg. Solanum tormm (Sundaikaai) and rarely trees (S. giganteum).

Root

A branched tap root system.

Stem

Aerial, erect, spinous eg. Solanum xanthocarpum (Kandangkathiri), herbaceous, woody, cylindrical, branched, hairy (eg. Petunia hybrida and Nicotiana alata). In S. tuberosum, the stem is modified into tuber.

Leaf

Petiolate, usually alternate, sometimes opposite, simple, entire (eg. Petunia hybrida), exstipulate and showing unicostate reticulate venation.

In S. xanthocarpum, the midrib and veins are found with yellowish spines.

Inflorescence

Solitary, axillary cyme (eg. Datura stramonium) or extra axillary scorpioid cyme called rhipidium (fan shaped cyme) as in S. nigrum or helicoid cyme as in S. tuberosum or umbellate cyme as in Withania somnifera.

Flower

Bracteate (eg. Petunia hybrida) or ebracteate

eg. S. nigrum (Manathakkaali), ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic (eg. Datura stramonium) or Zygomorphic (eg. Schizanthus pinnatus), bisexual and hypogynous.

Calyx

Sepals 5, green, gamosepalous, tubular and showing valvate aestivation

eg. Datura metal (Oomathai) or imbricate aestivation (eg. Petunia hybrida), bell shaped and persistent (S. melongena).

Corolla

Petals 5, gamopetalous, funnel shaped, rotate, tubular, usually plicate (folded like a fan blade) showing twisted or valvate or imbricate aestivation.

Androecium Stamens 5, epipetalous, alternate with the petals, usually not equal in length and filaments are inserted in the middle or basal region of corolla tube and basifixed.

Anthers dithecous, introrse, usually basifixed or dorsifixed, dehiscing longitudinally or through apical pores (eg. S.nigrum).

In Schizanthus pinnatus, two stamens are fertile and three stamens are reduced to staminodes.

Gynoecium

Ovary superior, bicarpellary and syncarpous. Ovary bilocular, carpels obliquely placed and ovules on axile placentation.

In Datura species, bilocule becomes tetralocular by the formation of false septa. Style simple and undivided. Stigma bifid or capitate.

Fruit

A berry or septicidal capsule. In Lycopersicon esculentum, the fruit is a berry and in species of Datura and Petunia, the fruit is a capsule.

Seed

Endospermous.

Botanical description of Datura metal – Solanaceae

Habit

Large, erect and stout herb.

Root

Branched tap root system.

Stem

The stem is hollow, green and herbaceous with strong odour.

Leaf

Simple, alternate, petiolate, entire or deeply lobed, glabrous showing unicostate reticulate venation and exstipulate.

Inflorescence

Solitary and axillary cyme.

Flower

Flowers are large, greenish white, bracteate, ebracteolate, pedicellate, complete, dichlamydeous, pentamerous, regular, actinomorphic, bisexual and hypogynous.

Calyx

Sepals 5, green, gamosepalous showing valvate aestivation. Calyx is mostly persistent and odd sepal is posterior in position.

Corolla

Petals 5, greenish white, gamopetalous, plicate (folded like a fan) showing twisted aestivation, funnel shaped with wide mouth and 10 lobed.

Androecium

Stamens 5, free from one another epipetalous, alternate the petals and are inserted in the middle of the corolla tube.

Anthers are basifixed, dithecous with long filament, introrse and longitudinally dehiscent.

Gynoecium

Ovary superior, bicarpellary and syncarpous.

Ovary basically bilocular but tetralocular due to the formation of false septa.

Carpels are obliquely placed and ovules on swollen axile placenta. Style simple, long and filiform. Stigma two lobed.

Spinescent capsule opening by four apical valves with persistent calyx.

Seed

Endospermous.

ECONOMIC IMPORTANCE OF Solanaceae

1. Food plants

Tubers of Solanum tuberosum (potato) are used as common vegetable throughout the world.

Tender fruits of S. melongena (brinjal) and ripened fruits of Lycopersicon esculentum (tomato) are used as delicious vegetables.

2. Medicinal plants

Roots of Atropa belladona yield powerful alkaloid ‘atropine’. It is used for relieving muscular pain.

Leaves and flowers of Datura stramonium are the sources of drug ‘stramonium’ used to treat asthma and whooping cough.

Leaves, flowers, berries of Solanum trilobatum (thoodhuvalai) are used to treat cough.

Roots and leaves of Withania somnifera (Amukkara) are used to treat nervous disorder and are diuretic apart from useful tonic.

3. Tobacco

Leaves of Nicotiana tabacum (tobacco) contain alkaloids nicotine, nornicotine and anabasine.

Nicotine is considered to be the principal alkaloid in commercial tobaccos such as cigarette, bidi, pipes and hukkah as well as chewing and snuffing.

It is also used as sedative, antispasmodic and insecticide.

4. Ornamental plants

Cestrum diurnum (day jasmine), C. nocturnum (night jasmine) and Petunia hybrida (pink flower) are grown in gardens for their beautiful flowers.

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QUESTION For Solanaceae:

What is atropine?
Give the systematic position of Solanaceae.
Write the binomials of any three medicinally useful plants in Solanaceae.
Describe the gynoecium of members of Solanaceae.
Write the different types of inflorescence found in Solanaceae. Give examples for each.
Draw the floral diagram and write the floral formula of Datura metal.
Write any three binomials of food plants of Solanaceae.
Name the alkaloids found in tobacco.
Give an account of the economic importance of the family Solanaceae.
Describe Datura metal in botanical terms.
Write the general characteristic features of Solanaceae.