In this article we will discuss about:- 1. General Characters of Rubiaceae 2. Floral Formula of Rubiaceae 3. Number and Distribution 4. Range of Floral Structures 5. Common Plants 6. Affinity and Economic Importance.
General Characters of Rubiaceae:
Plants—minute herbs (e.g., Galium) to huge trees (e.g., Anthocephalus). Leaves—opposite or whorled, simple, entire, usually with interpetiolar or less often with intrapetiolar stipules. Inflorescence—dichasial cymes, sometimes aggregated into heads (e.g., Anthocephalus, Morinda).
Flowers—usually regular, bisexual, epigynous. Sepals—(4-5), rarely unequal, valvate. Petals—(4-5), funnel- or salver-shaped or rotate, imbricate, valvate or twisted. Stamens— 4-5, alternating with petals, epipetalous, inserted on the corolla tube or at its mouth; anthers introrse, 2-celled.
Carpels—usually (2); ovary inferior, usually 2-celled, with numerous anatropous ovules in each cell on axile placenta (but 1-celled with parietal placenta, as in Gardenia). Fruit—capsule or berry (e.g., Coffea), sometimes aggregate (e.g., Morinda). Seed—with bony or horny endosperm. Embryo—straight or curved.
Floral Formula of Rubiaceae:
Number and Distribution of Rubiaceae:
This family consists of about 400 genera and 4,800 species extending from the tropical to the frigid regions.
Range of Floral Structures in Rubiaceae:
Flowers are generally bisexual, regular, tetra- or pentamerous; calyx with valvate aestivation; corolla usually funnel-shaped, salver- shaped or rotate with valvate, imbricate or contorted aestivation. Stamens inserted on the corolla-tube, 2-celled. Carpels (2), sometimes provided with a fleshy disc; ovary inferior, 1-many-celled, usually 2-chambered, with numerous to 1 anatropous ovules in each; style filiform, bifid or multifid.
Variation in the floral structure is also remarkable in the different genera. Regular flowers occur in Oldenlandia, Rondeletia, Cinchona, Ixora, Hamelia, but zygomorphy of flower is found in Posoqueria, Henriquezia.
Unisexuality is often noted in some genera. The dioecious flowers are found in Anthospermum, Coprosma.
Calyx becomes enlarged and leaf-like, as in Mussaenda, Warscewiczia and also in Nematostylis.
Ovary is generally inferior, but semi-inferior ovary is also found to occur in Synaptantha; the superior ovary is sometimes found in the genus Gaertnera (Tropical Africa and India) and Pagamea (Brazil-Guiana).
Variations in the number of chambers of ovary, number of ovules in each chamber, and attachment of ovules also occur in many genera. Exceptions to the two-chambered ovary with parietal placentation occur in the genera Gardenia, Oldenlandia, Rondeletia, Cinchona; Pavetta is uniovulate with the ovule sunken in the fleshy, funiculus. The genera Vangueria, Knoxia, Ixora, Hamelia, etc., represent the uniovulate one-chambered ovary.
The attachment of the ovules either at the base of the ovary or to the septum is variable in different genera. Basal attachment of ovules is found in the genera Psychotria (Uragoga), Hydnophytum, Myrmecodia, Paederia and others. Septal attachment of ovules is noted in some genera, such as, Galium, Asperula, Rubia, Crucianella and others.
Common Plants of Rubiaceae:
(1) Ixora coccinea L. and I. Parviflora Vahl. = I. arborea Roxb., are common garden shrubs.
(2) Oldenlandia corymbosa L., O. umbellata L. and O. paniculata L., are common weeds in rice-fields.
(3) Anthocephalus cadamba Miq. = A. indicus Rich., a common large tree.
(4) Adina cordifolia Hook. f.
(5) Cape jasemine (Gardenia florida Willd. = G. jasminoides Ellis.), a much-branched shrub grown in gardens.
(6) Vangueria spinosa Roxb. = Meyna laxiflora Robins, a spinous tree.
(7) Paederia foetida L., a foetid slender twining shrub, the leaves of which are reputed as a good stomachic.
(8) Indian madder (Rubia tinctoria L.), a climbing herb with big stipules.
(9) Mussaenda frondosa Hook., a small shrubby plant, one of the calyx-lobes of which grows out into a large white leaf-like expansion, common in nurseries.
(10) Catesbaea spinosa, a highly spinous herb with showy white tubular flowers which hang vertically downwards; very common in the Indian botanic garden.
(11) Coffee plant (Coffea arabica L.), usually cultivated in Southern India for coffee.
(12) Cinchona plant (Cinchona succirubra Pavon ex Klotzsch, C. officinalis L., C. ledgeriana Moens, C, calisaya Wedd.), cultivated on the hills for its bark which yields quinine.
(13) Ipecac (Psychotria ipecacuanha Stocks = Uragoga ipecacuanha Bail.), a medicinal plant with moniliform roots.
(14) Dentella repens Forst., a common weed.
(15) Morinda citrifolia L., a garden plant which produces, multiple fruit.
(16) Randia dumetorum Lamk., a large shrub with spines; R. uliginosa DC., a small tree that can be found in Indian Botanic Garden.
(17) Hamelia patens Jacq., a common garden plant.
(18) Stephegyne parvifolia Korth. = Mytragyna parvifolia Korth., often mistaken for Anthocephalus.
(19) Canthium angustifolium Roxb., a spreading shrub of the Sundribans.
(20) Hedyotis auricularia L., a herb.
(21) Uncaria macrophylla Wall., a strong climber.
(22) Wendlandia exserta DC., a small crooked tree.
(23) Anotis calycina Hook, f., a slender annual herb.
(24) Petunga roxburghii DC., an evergreen shrub of the Sundribans.
(25) Pavetta indica L., a small tree.
(26) Knoxia corymbosa WilId., a common erect annual.
(27) Spermacoce hispida L. = Borreria hispida K. Schum., a common perennial herb.
(28) Hamiltonia suaveolens Roxb., a small shrub.
Affinity and Economic Importance of Rubiaceae:
This family can be traced phylogenetically from Umbelliferae, particularly allied to Cornaceae, in the morphological aspects, such as, presence of interpetiolar stipules, cymose umbel-like inflorescence, suppression of calyx, epigyny, etc.
The family is also allied to Adoxaceae, Caprifoliaceae under the order Rubiales. Rubiaceae is apparently related to Compositae. The derivation of head can be traced from the head-like inflorescence of some members of Rubiaceae and Dipsaceae.
Economic Importance of Rubiaceae:
This family is of economic importance. Coffee is obtained from Coffea arabica. Quinine is obtained from the bark of Cinchona. Paederia, Oldenlandia and Anthocephalus are of medicinal importance. Psychotria ipecacuanha, which is the source of ‘vinum ipecac’, is also a valuable medicinal plant; the alkaloid ’emetine’ is extracted from the plant.
The roots and branches of Rubia tinctoria yield a red dye. Vangueria edulis is cultivated for fruits. Some plants are ornamentals, such as, Gardenia, Rubia, Ixora, Knoxia, Stephegyne, Catesbaea, Morinda, Mussaenda, Galium, Hamelia, Randia, etc.
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