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In this article we will discuss about:- 1. Characters of Meliaceae 2. Distribution of Meliaceae 3. Economic Importance 4. Affinities.
Characters of Meliaceae:
Plants woody trees, leaves pinnately compound exstipulate; leaflets asymmetrical, margin serrate, inflorescence cymose panicles, flowers actinomorphic, hermaphrodite, calyx and corolla sometimes united, stamens 8 to 10, monadelphous, obdiplostemonous: annular necticiferous disc between petals and stamens, gynoecium pentacarpellary, syncarpous, superior, fewer or multilocular with 1-2 rarely more ovules in each locule; single style; fruits various – capsular or drupaceous.
A. Vegetative characters:
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Habit:
Mostly woody trees rarely shrubs, often with a characteristic smell.
Roots:
Much branched tap root.
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Stem:
Woody much branched, erect, solid.
Leaves:
Alternate, exstipulate, pinnately compound rarely simple, without transparent dots or glandular dots, serrate margin.
B. Floral characters:
Inflorescence:
Cymose panicles often axillary.
Flower:
Pedicellate, bracteate, complete, hermaphrodite or polygamous, actinomorphic, hypogynous, pentamerous, with a necticiferous disc.
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Calyx:
Sepals 4-5, small poly- or gamoseplaous (connate at the base), imbricate rarely valvate aestivation, inferior.
Corolla:
Petals 4-5 rarely 3 to 8, polypetalous rarely connate at the base or adnate to the staminal tube, imbricate or twisted aestivation, inferior.
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Androecium:
Stamens 8-10, inserted outside the base of hypogynous disc, filaments united to form a columnar tube (monadelphous; Cedrela), anthers bithecous, erect, introrse, longitudinal dehiscence, necticiferous disc present or absent.
Gynoecium:
Carpels 2-5, syncarpous, superior, 2-5 locular, axile placentation, with 1-2 ovules in each loculus, single style, stigma capitate, discoid or lobed.
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Fruit:
Berry, capsule or drupe.
Seed:
Winged, albuminous or exalbuminous.
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Pollination:
Entomophilous, due to the presence of nectaries.
Floral formula:
Distribution of Meliaceae:
This family is also called Mahogany family. It includes 50 genera and 1400 species according to Willis. In India it is represented by 20 genera and 70 species. It is widely distributed in tropics of both the hemispheres.
Economic Importance of Meliaceae:
The family is not of great economic importance.
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1. Oil:
The seeds of Melia azadirachta (H. Neem) yield the ‘margossa’ oil of commerce. The oil is used in soap industry and medicinally in rheumatism and skin diseases. The oil of Carapa guianensis is used as an illuminant. The oil of Cedrela i.e., cedar oil is used in microscopy.
2. Medicines:
Almost every part of Melia azadirachta possesses some medicinal properties. The bark is a bitter tonic, astringent and antiperiodic. The bark, root bark and young fruits are used as a tonic antiperiodic and alterative. Leaves are used as poultice and applied to boils, the twigs as tooth brushes.
Decoction of leaves is antiseptic and used to wash ulcers and eczema. The oil is used in rheumatism and skin diseases. Dry flowers are used as a tonic and stomachic. It is blood purifier.
The bark of Cedrela tonna is used as astringent, tonic and antiperiodic in chronic dysentery.
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3. Timber:
The wood of Cedrela toona (H. Tun), is used for furniture, carving and also for cigar boxes. The Swietenia mahoganii, Khaya senegalensis produce cabinet wood.
4. Ornamentals:
Some of the plants viz., Melia, Amoora, Swietenia are grown in gardens.
Primitive characters:
1. Plants are mostly trees or shrubs.
2. Leaves alternate.
3. Presence of secretary cells.
4. Wood rays heterogenous.
5. Flowers hermaphrodite and hypogynous.
6. Flowers actinomorphic.
7. Calyx and corolla free.
8. Stamens free.
9. Pollination by insects.
Advance characters:
1. Leaves mostly compound.
2. Leaves exstipulate.
3. Unisexual flowers in Amoora, Lansium.
4. Flowers are small in size.
5. Inflorescence cymose or racemose.
6. Reduction in number of sepals and petals e.g. Amoora (3 sepals and 3 petals).
7. Androecium is monadelphouB.
8. Reduction in number of stamens (Melia 10-12, in Heynea 8-10, Cedrela 4-6, Amoora 3).
9. Gynoecium syncarpous.
10. Placentation axile.
11. Fruit simple.
12. Seed non-endospermic in many genera.
The family is regarded as one of the advance among Geraniales.
Affinities of Meliaceae:
Hallier placed the family in his order Terebinthales and considered that it is derived from Rutaceae. Both the families resembled each other in many characters viz., plants are mostly trees and shrubs, leaves exstipulate and compound, small scented flowers. Bessey, Engler and Prantl and Bentham and Hooker retained family Meliaceae in Geraniales.
Rendle has placed it as the last family of Rutales. Cronquist (1968) included this family under order Sapindales of sub-class Rosideae and class Magnoliatae. Takhtajan (1969) included Rutaceae and Meliaceae in order Rutales. Hutchinson included this family as the only family in his order Meliales.
Common plants of the family:
1. Melia azadirachta (H. Neem, Margosa tree) – contains margosic acid.
2. Cedrela toona (H. Tun., Indian Mahogany) – cultivated for wood; flowers yield dye called “Vasanti”.
3. Chloroxylon (stain wood) – valuable timber tree.
4. Carapa obovata – Small tree of Sundarbans.
5. Swietenia maliogani – beautiful tree with shining wood.
Division of the family and chief genera:
Engler divided the family into three sub-families as below:
I. Cedreioideae:
Stamens free, from capsule and seed winged. Cedrela.
II. Swietenioideae:
Stamens monadelphous, fruit capsule, seed winged, Swietenia, Khaya.
III. Melioideae:
Stamens monadelphous, fruit capsule, berry or drupe, seeds not winged. Melia.
Important Type of Meliaceae:
Melia azadirachta (Fig. 46.1):
Habit:
A perennial tree.
Root:
Tap, well branched, with deep feeders.
Stem:
Woody, erect, aerial, cylindrical, solid, branched, lower stem covered by bark.
Leaves:
Alternate, exstipulate, compound imparipinnate.
Leaflet:
Petiolate, ovate, serrate margin, acute apex, unicostate reticulate.
Inflorescence:
Axillary panicle.
Flower:
Pedicellate, complete, hermaphrodite, hypogynous, actinomorphic, pentamerous, white, scented.
Calyx:
Sepals 5, gamosepalous, green, valvate, inferior.
Corolla:
Petals 5, polypetalous, imbricate, white, inferior.
Androecium:
Stamens 10, monadelphous, forming a tube, with anthers at the top, on the inside, opposite the teeth of the staminal tube, basifixed, bithecous, inferior.
Gynoecium:
Tricarpellary to multicarpellary, syncarpous, superior, number of locules is equal to number of carpels, one or two ovules per locules, axile placentation; style long, stigma capitate, nectar disc below the ovary.
Fruit:
Drupe.
Seed:
Non-endospermic.
Floral formula:
