Let us learn about Family – Asclepiadaceae. After reading this article you will learn about: 1. Explanation on Family – Asclepiadaceae 2. Economic Importance of Family – Asclepiadaceae.
Explanation on Family – Asclepiadaceae:
According to Rendle there are about 280 genera and over 1800 species in this family.
Distribution:
The members of this family are mainly found in the tropical regions of the world. They occur specially in the drier parts of Central and South America.
In our country the family is represented by several genera, such as, Asclepias, Calotropis, Ceropegia, etc. Asclepias curassavica is commonly found in ‘sub-Himalayan tracts; Calotropis gigantea is commonly found in Northern India; Calotropis procera is quite common in the Punjab, Uttar Pradesh and Andhra Pradesh. The species of Ceropegia are commonly found in South India.
Habit:
The plants of this family are mostly erect herbs or woody climbers but some are succulent. The perennial herbs are quite common in the dry regions of South and Central Africa. Some plants perennate by means of tuber-like rhizomes. Large shrubs and trees are rarely found. Hoya is a plant of succulent habit; it possesses fleshy stem and leaves.
Stapelia is a native of South Africa. It is cactus like in habit possessing thick and fleshy stems; the leaves are reduced to thorns or scales. Dischidia is an epiphytic plant; it climbs upon its host by means of adventitious roots, the leaves are succulent and covered with a coating of wax. Cryptostegia grandiflora is a climbing shrub.
The species of Hemidesmus, Gymnema, Pergularia, etc., are also climbing shrubs. Leptadenia spartium is a shrub. Calotropis procera, (Verna.-Ali) is a xerophytic shrub and Calotropis gigantea (Verna.-Safed Ak) is a large shrub. Asclepias curassavica is a perennial herb.
The species of Ceropegia, Pentatropis, etc., possess underground tuber like parts. Tylophora indica is a herb. Most of the plants possess xerophytic characters and certain are extreme xerophytes.
Anatomically the plants of this family resemble with that of Apocynaceae. They also possess bicollateral bundles and the latex. According to Busich (1913), the endophytic mycorrhiza is frequently found in the roots of succulent plants of this family.
The species of Pentatropis possess tuberous roots; whereas Ceropegia tuberosa possesses tubers, by means of which, they perennate.
Leaves:
The leaves are simple, sub-sessile and exstipulate. In many cases the leaves are fleshy and covered with a coating of wax, e.g., Calotropis. In Stapelia, the leaves are very much reduced and represented by spines and scales.
Inflorescence:
The inflorescence is of two types, i.e.:
(1) Cymose and
(2) Racemose.
Generally the cymose type of inflorescence is found. In such cases the axis ends in a terminal flower, while branching occurs in the axils of the two branches forming a dichasial cyme, out one of the two branches of the dichasium grows faster than the other and ultimately one of the branches is completely suppressed and the inflorescence becomes monochasial cyme.
In certain cases the inflorescence is of racemose type. This is either a raceme or a umbel. Sometimes the flowers are found to be arranged in umbelliform cymes. When the inflorescence is axillary only one flower is found at each node; the other leaf either remains completely sterile or possesses a vegetative shoot.
In Calotropis, Asclepias the flowers are being arranged in umbellate cymes. In Hemidesmus, the flowers are found to be arranged in axillary cymes.
Flowers:
The flowers are pedicellate, bracteate, hermaphrodite, actinomorphic, rarely zygomorphic, e.g., in Ceropegia, complete. The general plan of the flower is pentamerous with three regularly alternating pentamerous whorls of calyx, corolla and androecium, however, the number of carpels is reduced to two in the gynoecium.
Usually the flowers are small in size, but the flowers of Ceropegia, Stapelia and Stephanotis are quite large in size.
Calyx:
It consists of five sepals, which are either free (polysepalous) or somewhat connate at the base; with the odd sepal posterior. The aestivation is quincuncial or rarely valvate.
Corolla:
It consists of five united petals (i.e., it is gamopetalous). The petals are spreading (i.e., rotate), but in Stephanotis the corolla tube is long, forming a salver-shaped corolla. In Ceropegia the corolla is pitcher-like in appearance (zygomorphic). The aestivation is contorted and rarely valvate.
Sometimes the petaloid appendages arise either from the corolla or from the back of the stamens. Very often these hairs or appendages are found inside or at the mouth of the corolla forming the corolline corona.
Androecium:
It consists of five stamens. The anthers are united laterally, giving rise to a five sided blunt cone, which is usually attached on the inside to the stigma head, except in the subfamily Periplocoideae. With the result of this union of anthers and pistils, the gynostegium is formed.
The pollen grains of each half anther associated in tetrads are found in a sac like structure known as pollinium. The anthers are almost quite sessile.
In the typical members of the family the translator consists of two parts:
(1) Corpusculum and
(2) A pair of arms.
The corpusculum is attached to the margin of stigma head between the anthers and the pair of arms is attached to the pollinia of the adjacent anther halves.
In the members of the sub family Periplocoideae the translator consists of a spoon or funnel- shaped structure in between each anther, terminating below in a sticky disc. The granular pollen grains form one half of each of the two adjacent anthers, on maturity, pour into the concave receptacle of the translator.
Certain appendages or horn-like projections are given out from the backs of the anthers, are known as cuculi, which secrete and store honey. These appendages form a corona known as staminal corona.
Gynoecium:
It consists of two carpels. The ovaries remain free, but styles unite to form a common swollen stigma-head. This stigma-head may be flat or somewhat conical and sometimes even beaked. The receptive surfaces of the stigma are situated on the edge or on the underside of it. The ovary is superior. The placentation is marginal with many ovules.
Fruit:
Generally it is a pair of follicles. Sometimes there is only one follicle, because of the suppression of the other.
Seed:
Usually the seeds are flat, ovate-oblong and are crowned by a fruit of hairs. These hairs facilitate the dispersal of the seeds by wind. The embryo is large.
There are two sub-families, which may be distinguished as follows:
1. Periplocoideae-The pollen grains are granulur and arranged in tetrads. The translators are spoon or funnel shaped.
2. Cynanchoideae-Pollen grains are in twos, found in pollinia. The translators are differentiated into a corpusculum and a pair of arms.
Pollination:
The pollination takes place strictly by means of the agency of insects. As an insect visits the flower, the sticky basal disc of translator turns outwards and adheres to the head of the insect visitor. The whole translator with its pollinia or pollen contents is carried over by the insect from one flower to another flower where the pollen grains are deposited on the stigmatic surfaces on the underside of the stigma-head.
In the sub family Cynanchoideae, where the pollinia are found the insect visiting the flower in the search of nectar pushes its leg in the slit left between the adjacent anthers, and when it pulls out the leg, it comes in contact with the notched base of the corpusculum, and this way the complete translator with two pollinia is dragged out.
At first the pollinia are quite apart from each other, but as the hygroscopic arms of the translator are dried up they become close to each other. If this insect visits another flower, the pollinia are readily pushed into one of the slits, and will slip into the stigmatic chamber, thus effecting cross- pollination. Chiefly the pollination is by two-winged flies.
Description of important plants in semi-technical language:
1. Calotropis procera-, Verna. Ak:
Habit:
A shrub, about 3 to 6 feet high, younger parts and the under surface of the leaves covered with white waxy secretion, all parts contain milky latex.
Stem:
Erect, branched, glabrous, woody below and herbaceous above, tomentose, solid, cylindrical.
Leaf:
Simple, cauline, sessile, opposite decussate, exstipulate, 2-5 in., long, thick, glaucous- green, elliptical or obovate oblong with cordate or often amplexicaul base, acute or shortly acuminate, unicostate reticulate venation.
Inflorescence:
Cymose, umbellate cyme.
Flower:
Pedicellate, bracteate, hermaphrodite, actinomorphic, regular, complete, pentamerous except pistil, hypogynous.
Calyx:
5 sepals, polysepalous or connate at the base, greenish, lobes lanceolate, acute apex, interior quincuncial aestivation.
Corolla:
Petals, gamopetalous, pink or whitish with purple spots, lobes spreading, inferior, twisted aestivation.
Androecium:
Five stamens, filaments connate in a fleshy staminal tube around the ovary, the apex of the staminal tube united with the much-dilated stigmatic head to which the anthers are also coherent, forming the pentagonal gynostegium; anthers short, broad tipped with inflexed membranous flaps, bi-celled, the pollen grains of each cell aglutinated into sac like pollinium; the pollinia of each anther are united together by means of short stalks or caudicles to a distinct dark coloured dot-like structure, the corpusculum, which lies at the angle of the gynostegium, thus forming a translator apparatus.
Gynoecium:
2 carpels (bicarpellary), syncarpous; the pistil free below and fused above; two distinct ovaries end in two styles forming a pentangular stigmatic head to the sides of which the anthers are coherent; ovary superior, unilocular, many ovules, marginal placentation.
Fruit:
A pair of follicles.
Seeds:
Mainly, broadly ovate, flat tomentose with tuft of silky hairs.
2. Asclepias curassavica:
Habit: An erect perennial herb.
Stem: Erect, branched, herbaceous, solid, cylindrical.
Leaves: Simple, opposite, short petiolate, exstipulate, linearlanceolate, entire, acute, unicostate reticulate venation.
Inflorescence: Cymose, umbellate cyme.
Flowers: Pedicellate, purple-yellow, small bisexual, actinomorphic, hypogynous.
Calyx: 5 sepals, polysepalous, imbricate aestivation.
Corolla: 5 petals, gamopetalous, twisted aestivation,
Androecium: Similar to that of Calotropis procera. The filaments attached to the base of the corolla are united to form a column around the pistil, the anthers being pressed close to the styles; each stamen bears on the side away from the pistil an appendage which enfolds the anther like a hood; these appendages collectively form a corona.
Gynoecium: 2 carpels (bicarpellary), syncarpous, ovary superior.
Fruits: Follicle.
3. Cryptostegia grandiflora R:
Br.; Verna. Vilayati vakhandi; Eng. Rubber vine:
Habit:
A perennial twiner.
Root:
Tap and branched.
Stem:
Herbaceous, lower part woody, aerial, weak, climbing, branched, twiner, solid, cylindrical, rough, green, latex present, nodes and internodes prominent.
Leaf:
Ramal and cauline, opposite decussate, exstipulate, simple, petiolate elliptic ovate, entire, acute, coriaceous, glaucous, unicostate reticulate.
Inflorescence:
Cymose dichasial cyme.
Flower:
Bracteate, bracteolate, pedicellate, actinomorphic, regular, hermaphrodite, pentamerous, hypogynous, cyclic.
Calyx:
5 sepals, polysepalous, quincuncial aestivation, green, margins membranous.
Corolla:
5 petals, gamopetalous, twisted, coronary outgrowths present, violet.
Androecium:
5 stamens, polyandrous, epipetalous, dithecous, introrse; pollen grains are being shed from each anther lobe and are deposited in the translator. Each spoon-shaped translator is found to be situated in between two stamens.
Gynoecium: 2 carpels (bicarpellary), ovary superior, ovaries free but style and stigma fused, many ovules in , each locule, marginal placentation, style short, stigma globular.
Economic Importance of Family – Asclepiadaceae:
The family is of little economic value. Some plants are ornamental while certain others are of medicinal value.
A list of few important plants is given below:
1. Asclepias curassavica; Eng.-Blood flower; Verna-Kakatundi-This is a perennial herb or a small shrub. It is cultivated as an ornamental. The plant is of medicinal value. The root is used as a purgative and as a medicine for piles.
2. Calotropis gigantea; Eng.-madar; Verna-Ak-A perennial undershrub. The floss, obtained from the seed, is used for stuffing purpose. The stem yields a fibre. All parts of the plant are used medicinally. The fresh leaves are used in the fomentation for swellings. The gun powder charcoal is prepared from the wood. It is commonly found in Northern India.
3. Calotropis procera; Syn. Asclepias gigantean; Eng. Akund; Verna-Safed Ak.-The stem fibre is made into cordage and the floss from the seed is used as a stuffing material. The stem and leaves are used medicinally several ways. It is commonly found in Andhra Pradesh and the Punjab.
4. Ceropegia hirsuta; Verna-Khantodi-This is a climbing shrub. The tubers are edible. It is commonly found in Tamil Nadu, Travancore and Andhra Pradesh.
5. Ceropegia tuberosa: Verna.-Patala tumbi—The tubers are edible. It is commonly found in Tamil Nadu and Andhra Pradesh.
6. Ceropegia oculata; Verna.-Khantodi-The tubers are edible. It is a herb, found in South India.
7. Ceropegia lawii, Verna-Kharpundi-The tubers are edible. It is a succulent herb. Found in South India.
8. Cryptolepis buchanani; The plant produces a floss which is used as a stuffing material.
9. Cryptostegia grandiflora: Verna.-Vilayati-vaknandi-This is a beautiful climbing shrub with red-rose flowers, grown as ornamental.
10. Daemia extensa; Syn. Pergularia extensa; Verna-Utsan-A fibre is obtained from its stem. The juice of leaves is used medicinally in several ways, e.g., as the remedy of diarrhoea, asthama, etc.
11. Dischidia rafflesiana; Verna-Bandikuri-This is an epiphytic undershrub. The roots are chewed as a remedy for coughs.
Economic value:
Grown as an ornamental plant for its beautiful violet-coloured flowers. The leaves are toxic.
12. Gymnema sylvestre; Verna.-Gurmar-This is a large climbing shrub. The flowers are found to be arranged in umbellate cymes. The roots are used as antidote for snake-bite. The leaves are used as remedy for diabetes.
13. Hemidesmus indicus; Eng. -Indian sarsaparilla; Verna.-Magrabu-This is a twining shrub. The roots are used as a tonic, which is useful in loss of appetite, fever, skin diseases, as blood purifier, rheumatism and snake-bite. The tonic (sarsaparilla) is diuretic diaphoretic and demulcent.
14. Oxyrstelma esculentum; Verna-Dudhialata-The fruits are edible; the plant possesses medicinal properties. The latex is used to wash ulcers. The medicine for scabies is prepared from it.
15. Pentatropis cynanchoides, Verna-Kanathodi-The tuberous roots are edible.
16. Periploca aphylla-, Verna-Barri-The stem yields a fibre for cordage; the latex is applied to swellings and tumours, it is used as a purgative; sometimes the flowers are eaten.
17. Leptadenia pyrotechnica; Syn. L. spartium-This, is a shrub found in the Punjab, Uttar Pradesh, Rajasthan and Gujarat. The slimy fruits and young twigs are eaten as vegetable.
18. Tylophora indica; Verna-Antamul-This is a herb. Its leaves and roots are used as substitute for ipecacuanha. This is also used as emetic, diaphoretic and expectorant. The plants are commonly found in Bengal, Assam and South India.
19. Sarcostemma acidum; Verna-Somlata-This is a leafless shrub, commonly found in dry areas of Andhra Pradesh, Tamil Nadu, and Karnataka. It is used to destroy white ants from sugarcane fields.
20. Caralluma fimbriata; Verna-Makedshingi-This is a fleshy herb, eaten as a vegetable. It is mainly found in Andhra Pradesh.
21. Cynanchum arnottianum; This is a herb whose dried leaves are used to destroy maggots. It is found in Kashmir.
22. Cosmostigma racemosum-This is a climbing shrub, found in the Western Ghats, Karnataka and Andhra Pradesh. The Leaves are used to cure ulcerous sores.
Systematic Relationships:
The various systems of classification differ in their interpretation of the limits of the order Gentianales. Bentham and Hooker included six families in this order. They are-Oleaceae, Salvadoraceae, Apocynaceae, Asclepiadaceae, Loganiaceae and Gentianaceae.
Engler and Diels called the Gentianales the Contortae having six families, i.e., Oleaceae, Desfontaineaceae, Loganiaceae, Gentianaceae, Apocynaceae and Asclepiadaceae.
Wettstein and Rendle restricted the Contortae to contain five families but Oleaceae. They placed the Oleaceae within Oleales. Hutchinson has placed the families of Contortae into three separate orders. The Loganiales consists of Loganiaceae and Oleceae; Apocynales of Apocynaceae and Asclepiadaceae and Gentianales of Gentianaceae.
Originally Engler included the Salvadoraceae in the order Contortae, but later on (Engler and Gilg, 1924) this was transferred to the Sapindales.
The Asclepiadaceae have close affinities with Apocynaceae, Hutchinson considered that the Apocynaceae have been derived from stocks ancestral to the Loganiaceae.