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In this article we will discuss about:- 1. Characters of Convolvulaceae 2. Distribution of Convolvulaceae 3. Economic Importance 4. Affinities 5. Important Types.
Characters of Convolvulaceae:
Herbs or shrubs, climbing; leaves alternate, simple, exstipulate, rarely stipulate; inflorescence cymose; flowers actinomorphic, hermaphrodite, hypogynous; calyx 5, polysepalous; colrolla gamopetalous, campanulate; stamens 5, epipetalous, alternipetalous, disc present; ovary bicarpellary, syncarpous, superior, axile placentation, generally two ovules per loculus; fruit capsule or nut.
A. Vegetative characters:
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Habit:
Herbs (Convolvulus, Evolvulus), shrubs and climbing {Ipomoea, Argyeria), the plants may be xerophytic, hydrophytic (Ipomoea aquatica) or parasitic (Cuscuta).
Root:
Tap, branched, fleshy (Ipomoea batatus; H. Sakarkand). Cuscuta without ordinary roots but adventitious haustoria are present.
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Stem:
Erect, or prostrate, herbaceous, twiner (Ipomoea and Cuscuta), cylindrical, branched, solid or fistular, tuberous rhozomatous (Convolvulus).
Leaves:
Alternate, simple, exstipulate, petiolate, entire or palmately lobed, or pinnately divided (Quamoclit pinnata), unicostate or multicostate reticulate venation.
B. Floral characters:
Inflorescence:
Solitary axillary (Convolvulus, Evolvulus) or cymes.
Flower:
Bracteate, bracteolate, pedicellate, complete hermaphrodite, actinomorphic, pentamerous, (in Hildebrandita the flowers are tetramerous, unisexual) and hypogynous.
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Calyx:
Sepals 5, polysepalous rarely gamosepalous, persistent, imbricate, inferior.
Corolla:
Petals 5, gamopetalous, campanulate, or infundibuliform, imbricate, or valvate (induplicate valvate in Ipomoea), inferior.
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Androecium:
Stamens 5, polyandrous, epipetalous, length of the filaments variable in the same flower; dorsifixed or basifixed, inserted deep in the corolla tube, dithecous and introrse.
Gynoecium:
Bicarpellary, syncarpous, superior, situated on a disc, sometimes tetralocular, axile placentation, two or rarely one ovule per loculus; style simple, or two (Cuscuta), filiform, stigma capitate or bifid (Convolvulus, Ipomoea palmata).
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Fruit:
Capsule (Convolvulus, Evolvulus, Cuscuta) or berry.
Seed:
Endospermic.
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Pollination:
Entomophilous.
Floral formula:
Distribution of Convolvulaceae:
It is commonly known as “Sweet-potato family”. It includes 55 genera and 1650 species which are found in tropical region of the world. In India the family is represented by 177 species belonging to 20 genera.
Economic Importance of Convolvulaceae:
1. Food:
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Tuberous roots of Ipomoea batatus (Sweet potato) are rich in starch and edible. Root stock of Calystegia sepium are cooked and eaten. The leaves of Ipomoea aquatica are used as vegetable.
2. Medicinal:
Due to the purgative property of latex, several species are used as medicine (Exogynum purga). Ipomoea hederacea yields Kaladana. Leaves of Ipomoea pescarpae are boiled and applied externally in case of colic while decoction in used as a blood purifier and in bilious disorders. Ipomoea paniculata is considered good for rejuvenation, Merremia tridentata is used in rheumatism, piles and urinary disorders.
3. Weed:
Convolvulus arvensis, Evolvulus alsinoides, are the common weeds. Cuscuta is a parasite and ruins many types of plants.
4. Ornamental:
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Ipomoea biloba, Convolvulus, Porana, Calystegia apd Quamoclit are cultivated as ornamentals.
Primitive characters:
1. Presence of shrubs and woody climbers.
2. Leaves simple and alternate.
3. Solitary axillary inflorescence.
4. Flowers actinomorphic, hermaphrodite and hypogynous.
5. Calyx mostly free.
6. Stamens polyandrous and dithecous.
7. Seeds endospermic.
Advanced characters:
1. Plants mostly herbs annual or perennial.
2. Leaves reduced and scale-like in Cuscuta.
3. Parasitic habit.
4. Leaves exstipulate.
5. Corolla gamopetalous.
6. Number of stamens five; epipetalous.
7. Gynoecium with two fused carpels.
8. Fruit simple.
Affinities of Convolvulaceae:
Convolvulaceae is closely related to the Boraginaceae but can be distinguished by the terminal bilobed stigma, disc below the ovary and curved embryo.
Rendle and Wettestein segregated the family in a separate order Covolvulales, Wettestein considered them to be allied to the Malvales and Geraniales.
Common plants of the family:
1. Ipomoea:
Largest genus of the family; twining or erect herb, or shrub.
2. Cuscuta (H. Akash bel):
Parasitic, leafless twiner.
3. Convolvulus:
Common weed in the fallow fields.
4. Argyeria roxburghi:
Robust, beautiful climber with red, funnel-shaped flowers.
5. Argyeria nervosa (Elephant climber):
Garden climber with cordate leaves.
6. Evolvulus:
Sleeping, perennial herb, common on sandy soil.
7. Merremia:
Climbing or creeping shrub with cord-like stem rooting at the nodes.
8. Ipomoea biloba (Goats foot):
A sand binder.
Division of the family and chief genera:
The family is divided into 2 sub-families as follows:
Sub-family 1. Convolvuloideae:
The plants are autotrophic and bear leaves; cotyledons plicate. It includes 8 tribes, viz., Dichondreae, Dicranostyleae, Hidenbrandtieae, Convolvuleae, Poraneae, Ipomoeae, Argyerieae and Erycibrae.
Sub-family 2. Cuscutoideae:
Parasitic members with reduced scale leaves; cotyledons are either absent or reduced; Cuscuta.
Important Types of Convolvulaceae:
1. Ipomoea palmata (Fig. 77.1):
Root:
Tap, branched.
Stem:
Thin, cylindrical, greenish, climbing, perennial with distinct nodes and internodes solid, herbaceous.
Leaf:
Alternate, exstipulate, palmately compound divided into 5-7 leaflets, petiolate, leaves ovato-elliptical, entire, acute, unicostate reticulate.
Inflorescence:
A dichasial cyme.
Flower:
Bracteate, pedicellate, complete, hermaphrodite, pentamerous, hypogynous, violet coloured.
Calyx:
Sepals 5, polysepalous, green, quincuncial, inferior.
Corolla:
Petals 5, gamopetalous, infundibuliform, induplicate valvate.
Androecium:
Stamens 5, polyandrous, epipetalous, filaments of unequal length, slender, basifixed, dithecous, introrse.
Gynoecium:
Bicarpellary, syncarpous, superior, bilocular, axile placentation, with 2 ovules per locule, style slender long, stigma bilobed.
Fruit:
Capsule.
Floral formula:
2. Cuscuta reflexa (Fig. 77.2):
Habit:
A perennial herb, leafless, total parasite.
Root:
Absent, haustoria present.
Stem:
Weak, herbaceous, twining, branched, cylindrical, solid, smooth, yellowish green.
Leaves:
Absent.
Inflorescence:
Racemose or fasciculate.
Flower:
Bracteate, pedicellate, complete, hermaphrodite, actinomorphic, pentamerous, hypogynous, white.
Calyx:
Sepals 5, polysepalous; or slightly fused at the base, green, quincuncial, greenish white; inferior.
Corolla:
Petals 5, gamopetalous, campanulate, corolla teeth or lobes acute, reflexed, imbricate; corona like scales present at the base of corolla tube, inferior.
Androecium:
Stamens 5, polyandrous, epipetalous, filaments short, anthers dorsifixed, dithecous, introrse, inferior.
Gynoecium:
Bicarpellary, syncarpous, superior, bilocular, axile placentation, 2 ovules per loculus; style reduced; stigma bifid.
Fruit:
Capsule.
Floral formula:
3. Convolvulus arvensis:
Habit:
A trailing herb in sandy places and fields.
Root:
Tap, branched.
Stem:
Weak, aerial, herbaceous, trailing, solid, cylindrical, branched, green, hairy.
Leaves:
Cauline, ramal, alternate, simple, exstipulate, petiolate, linear lanceolate, entire, glabrous, acute, unicostate reticulate.
Inflorescence:
Cymose clusters.
Flower:
Bracteate, pedicellate, complete, hermaphrodite, actinomorphic, pentamerous, hypogynous, bluish white.
Calyx:
Sepals 5, polysepalous, persistent, green, inferor.
Corolla:
Petals 5, gamopetalous, infundibuliform, induplicate valvate, tube short, limbs spreading.
Androecium:
Stamens 5, polyandrous, epipetalous, filaments long, attached deep in the tube, unequal in length, anthers basifixed, dithecous, introrse.
Gynoecium:
Bicarpellary, syncarpous, superior, seated on a nectariferous disc, bilocular, axile placentation, ovules 2 per loculus, or simple, style stigma two.
Fruit:
A capsule opening by four valves.
Floral formula:
