DICOT FAMILIES

MALVACEAE – the cotton family

Systematic position
Class: Dicotyledonae
Sub-class: Polypetalae
Series: Thalamiflorae
Order: Malvales
Family: Malvaceae

General characters
Distribution

This family includes 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 represented by 22 genera and 125 species.

Habit

Plants may be annual herbs ( eg. Malva sylvestris) or perennial shrubs (eg. Hibiscus rosa-sinensis) or trees (eg. Thespesia populnea). The members of this family have mucilagenous substance. Stellate hairs occur on their young parts.

Root

Tap root system.

Stem

Aerial, erect (eg. Malva sylvestris), branched, woody (eg. Thespesia populnea), decumbent as in Malva rotundifolia (Thirikalamalli) and usually covered with stellate hairs.

Leaf

Petiolate, simple, entire (eg. Thespesia populnea) or palmately lobed (eg. Gossypium arboreum), alternate, stipulate, margins usually toothed (eg. Hibiscus rosa-sinensis) and showing reticulate venation.

Inflorescence

Solitary, terminal (eg. Malvastrum coromendelia) or solitary, axillary (eg.Thespesia populnea) or terminal or axillary cyme.eg.Pavonia odorata
(Peramutti).

Flower

Bracteate or ebracteate, bracteolate or ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic, regular, bisexual and hypogynous.

Epicalyx

Bracteoles forming a whorl outer to calyx is called epicalyx. Bracteoles 3 in Malva sylvestris, 5 to 8 in Hibiscus rosa-sinensis, 10 to 12 in Pavonia odorata and absent in Abutilon indicum.

Calyx

Sepals 5, green, gamosepalous showing valvate
aestivation. Corolla
Petals 5, coloured, polypetalous but slightly fused at the base due to adhesion with staminal tube, regular and showing twisted aestivation.

Androecium

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

Gynoecium

Ovary superior, two to many carpels but usually 5 to 10 carpels and syncarpous. Ovary with two to many locules. Pentacarpellary in Hibiscus rosa-sinensis, 10 in Althaea and 15 to 20 in Abutilon indicum. Number of locules usually corresponds to number of carpels. Each locule contains one to many ovules on axile placentation. Style long, slender and passes through the staminal tube ending in two to many distinct round stigmas.

Fruit

Loculicidal capsule e.g. Abelmoschus esculentus or schizocarp as in Abutilon indicum and Sida cordifoliaI (Nilathuthi).

Seed

Endosperm is scanty, covered with hairs as in Gossypium barbadense.

Botanical description of Hibiscus rosa sinensis

Habit
Perennial shrub.

Root
Tap root system.

Stem
Aerial, erect, cylindrical, woody and branched.

Leaf
Simple, Alternate, petiolate, stipulate, serrate, glabrous, apex acuminate with multicostate reticulate venation.

Inflorescence
Solitary cyme and axillary.

Flower
Pedicel jointed, bracteate, bracteolate, bisexual, large, showy, pentamerous, dichlamydeous, actinomorphic, complete and hypogynous and mucilage is present in floral parts.

Epicalyx
5 to 8 bracteoles outer to the calyx. They are green and free.

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

Corolla
Petals 5, variously coloured, polypetalous but fused at the base and showing twisted aestivation.

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

Floral diagram
Hibiscus rosa sinensis

Gynoecium

Ovary superior, pentacarpellary and syncarpous. Ovary pentalocular with many ovules per locule on axile placentation. Style simple, long, slender and passes through the staminal tube. Stigma 5, capitate and coloured.

Fruit
Mostly abortive.

ECONOMIC IMPORTANCE

1. Fibre plants

Gossypium barbadense (Egyptian cotton), G. hirsutum (American cotton), G. herbaceum (Cotton) and several other species of Gossypium yield cotton fibres of commercial value. The fibres are obtained from the surface of seeds. Hibiscus cannabinus (Deccan hemp) yields bast fibres which are used for making ropes.

2. Food plants
The tender fruit of Abelmoschus esculentus (lady’s finger) is used as vegetable. The leaves and sepals of Hibiscus sabdariffa (A kind of ‘pulichai’) are used for making pickles, jam and jelly. A delicious ‘chutney’ is prepared from the leaves and sepals of H. cannabinus (Pulichai keerai) and H. sabdariffa.

3. Timber Plants
Timber obtained from Thespesia populnea (portia tree) is useful for making boat, furniture and agricultural implements.

4. Medicinal plants
Root and leaves of Abutilon indicum (Thuthi) and Malva sylvestris are used against fever. Roots of Malva sylvestris and Althaea rosea are used for treating whooping cough and dysentery respectively.

5. Ornamental plants
Althaea rosea (Hollyhock), Hibiscus rosa sinensis (Shoe flower) H schizopetalus (A kind of shoe flower with dissected petals) are grown in gardens.

QUESTION:

1. Mention the systematic position of Malvaceae.
2. Write a note on androecium of Hibiscus rosa sinensis.
3. Describe the gynoecium of Hibiscus rosa sinensis.
4. Name any three fibre plants of Malvaceae.
5. Mention the binomial of any three medicinal plants of
6. Write any three binomials of food plants of Malvaceae.
7. Draw the floral diagram and write the floral formula of Hibiscus rosa sinensis.
8. What is epicalyx? It is present in Abutilon indicum?
9. Give a detailed account on economic importance of Malvaceae.
10. Describe Hibiscus rosa-sinensis in botanical terms.
11. List out characteristic features of members of Malvaceae.