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  DICOT Families

Introduction to DICOT Families

MALVACEAE - the cotton family

Systematic position

Class: Dicotyledonae

Sub-class: Polypetalae

Series: Thalamiflorae

Order: Malvales

Family: Malvaceae

General characters

Distribution

This family involves about 82 genera and more than 1,500 species. The plants are cosmopolitan in distribution, more abundant in tropical and subtropical regions.  In India, Malvaceae is presented through 22 genera and 125 species.

Habit

Plants might be annual herbs (example Malva sylvestris) or perennial shrubs (example Hibiscus rosa-sinensis) or trees (example Thespesia populnea). This family's members of have mucilagenous substance. Stellate hairs take place on their young parts.

Root

Tap root system.

Stem

  • Aerial,
  • Erect (example Malva sylvestris),
  • Branched,
  • Woody (example Thespesia populnea),
  • Decumbent as in Malva rotundifolia (Thirikalamalli) and generally covered with stellate hairs.

Leaf

  • Petiolate,
  • Simple,
  • Entire (example Thespesia populnea) or palmately lobed (example Gossypium arboreum), alternate,
  • Stipulate,
  • Margins generally toothed (example Hibiscus rosa-sinensis) and displaying reticulate venation.

Inflorescence

  • Solitary,
  • Terminal (example Malvastrum coromendelia) or solitary,
  • Axillary (example Thespesia populnea) or terminal or axillary cyme. Example Pavonia odorata (Peramutti).

Flower

  • Bracteate / ebracteate,
  • Bracteolate or ebracteolate,
  • Pedicellate, dichlamydeous,
  • Pentamerous,
  • Complete,
  • Actinomorphic,
  • Regular,
  • Bisexual and hypogynous.

Epicalyx

Bracteoles creating a whorl outer to calyx are termed as epicalyx. Bracteoles 3 in Malva sylvestris, 5 to 8 in Hibiscus rosa-sinensis, 10 to 12 in Pavonia odorata and not present in  Abutilon indicum.

Calyx

  • Sepals 5,
  • Green,
  • Gamosepalous displaying valvate aestivation.

Corolla

Petals 5, coloured, polypetalous but little fused at the base because of adhesion with staminal tube, regular and displaying twisted aestivation.

Androecium

Several stamens, filaments are fused to create a staminal tube around the style and monadelphous.  The staminal tube is fused along with the petals at their bases.  Anthers are monothecous, reniform, transversely that attached to filaments and transversely dehiscent.

Gynoecium

Ovary superior, two to several carpels but generally 5 to 10 carpels and syncarpous. Ovary with two to several locules. Pentacarpellary in Hibiscus rosa-sinensis, 10 in Althaea and 15 to 20 in Abutilon indicum. No. of locules generally corresponds to no. of carpels.   Each locule consists of one to several ovules on axile placentation.  Style long, slender and passes by the staminal tube ending in two to several distinct round stigmas.

Fruit

Loculicidal capsule example Abelmoschus esculentus or schizocarp like in Abutilon indicum and Sida cordifoliaI (Nilathuthi).

Seed

Endosperm is scanty that covered with hairs like in Gossypium barbadense.

Botanical explaination of Hibiscus rosa-sinensis

Habit

Perennial shrub.

Root

Tap root system.

Stem

  • Aerial,
  • Cylindrical,
  • Erect,
  • Woody and branched.

Leaf

  • Simple,
  • Serrate,
  • Glabrous,
  • Alternate,
  • Petiolate,
  • Stipulate apex acuminate with multicostate reticulate venation.

Inflorescence

Solitary axillary and cyme

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Flower

  • Pedicel jointed,
  • Bracteate,
  • Large,
  • Showy,
  • Pentamerous,
  • Bracteolate,
  • Bisexual,
  • Dichlamydeous,
  • Actinomorphic,
  • Complete and
  • Hypogynous and
  • Mucilage exists in floral parts.

Epicalyx

Five to eight bracteoles outer to the calyx.  They are free and green and.

Calyx

Sepals 5, green, gamosepalous displaying valvate aestivation and odd sepal is posterior in position.

Corolla

  • Petals 5,
  • Coloured variously,
  • Polypetalous but fused at the base and displaying twisted aestivation.

Androecium

Numerous stamens, monadelphous, filaments are fused to create a staminal tube around the style. Staminal tube is red in color.  Anthers are monothecous, reniform, yellow, transversely attached to the filament, dehisce transversely and extrorse.

 

Diagram: Hibiscus rosa-sinensis

Gynoecium

Ovary superior, pentacarpellary and syncarpous. Ovary pentalocular along with several ovules per locule on axile placentation.  Style simple, long, slender and passes via the staminal tube. Stigma 5, coloured and capitates.

Fruit

Mainly abortive.

Floral  Formula

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