Module on. TAXONOMY AND DIVERSITY OF RUTACEAE By. Dr Shabana Aslam

Transcription

1 Consortium for Educational Communication Module on TAXONOMY AND DIVERSITY OF RUTACEAE By Dr Shabana Aslam Lecturer, Botany Govt. Girls Higher Secondary School Rainawari,Cell No: e. mail:

2 TEXT The family Rutaceae, commonly known as Rue/Citrus family, is based on the type genus Ruta comprising the strong-scented Eurasian herbs. The family includes some of the most important fruit-bearing plants belonging to the genus Citrus such as our present day oranges, lemons, grapefruits, etc. The family is characterized by the occurrence of trees and shrubs which are often aromatic, containing alkaloids and phenolic compounds, and bearing compound gland-dotted leaves. The presence of pellucid glands filled with essential oils is a characteristic feature of the family. The common genera of this family are: 1. Citrus: Cultivated for fruits. 2. Aegle: Leaves are obligatory for the worship of Hindu God, Shiva. 3. Murraya: Leaves, roots and barks are used for flavouring curries. 4. Zanthoxylum: Prickles are present all over the plant body. 5. Ruta: Whole plant is aromatic. 6. Feronia: Fruits are of the size of tennis ball. I. Taxonomy of Rutaceae HABITAT: Plants are mesophytic. HABIT: The plants are nearly evergreen trees and shrubs, sometimes perennial herbs, rarely climbers, sometimes armed, often aromatic, with volatile oils. ROOT: Branched tap-root, often infected with a fungus. STEM: Erect, woody and branched, usually aromatic, often with spines or thorns (species of Aegle, Citrus). LEAVES: Usually alternate (Aegle, Citrus), rarely opposite (Evodea), simple (Calodendron) or compound; when compound,

3 leaves pinnate (Murraya) or palmate (Aegle), rarely unifoliate compound with winged petioles (Citrus); sometimes reduced to spines, petiolate, exstipulate, nearly always gland-dotted (except, Leptothyrsa, Phellodendron); aromatic. INFLORESCENCE: Usually cymose, sometimes axillary or terminal solitary (Triphasia), or racemose (Atalantia), corymbs, panicles or racemes. FLOWER: Bracteate, bracteolate (Ruta) or ebracteolate, bisexual or rarely unisexual (Toddalia, Evodea, Zanthoxylum), actinomorphic or rarely zygomorphic (Dictamnus, Cusparia), pentamerous or tetramerous (Acronychia), rarely trimerous (Triphasia), hypogynous or perigynous; a nectariferous disc present between stamens and ovary, varying from an apparent receptacular swelling to a cup-like structure. PERIANTH: Biseriate with distinct calyx and corolla, calyx rarely minute and inconspicuous. CALYX: Sepals commonly 4-5 (rarely 3), distinct (polysepalous) (Ruta) or basally connate (gamosepalous) (Murraya), regular, valvate or imbricate, rarely wanting as in some species of Zanthoxylum. COROLLA: Petals 4-5 (sometimes 3), rarely wanting as in some species of Zanthoxylum, usually distinct (polypetalous), rarely connate (gamosepalous) as in Correa and Almeidea, imbricate or rarely valvate; regular or unequal but not bilabiate. ANDROECIUM: stamens 8 or 10, rarely numerous (Citrus and Aegle) usually obdiplostemonous, filaments free or mono- or poly-adelphous, anthers dithecous, introrse, longitudinal in dehiscence; stamens of outer whorl occasionally reduced to staminodes (Tetractomia). GYNOECIUM: Carpels usually 4-5, rarely less or indefinite, united or (syncarpous) sometimes free (apocarpous) at base and united

4 above by styles; ovary superior, usually deeply-lobed, typically 4-5-loculed, with one or two ovules in each locule; styles free and as many as the carpels, or united; placentation axile, rarely parietal (Feronia); ovules anatropous or hemianatropous. FRUIT: Fruit is a hesperidium--characteristic to the family (Citrus), capsule (Ruta, Flindersia), samara (Ptelea), drupe (Skimmia) or rarely a winged berry, schizocarp or follicle. SEED: Endospermic or non-endospermic, with curved or straight embryo; cotyledons 2, flat, folded, or rolled; polyembryony with as many as 13 embryos (Citrus) is common; Citrus unshiu shows 40 embryos per seed. POLLINATION: Entomophilous. Insects like flies, bees, etc., are attracted by the coloured petals and the nectar secreted by the disc. SEED DISPERSAL: Dispersal of seeds occurs mainly by animals and human agencies. FLORAL FORMULA: Br,,,K 4-5 or (4-5),C 4-5 or (4-5),A 8-10 or α, G (4-5) or α.

5 Fig. 2: A generalized V.S of the flower. FLORAL DIAGRAM:

6 Fig.2: A generalized floral diagram of the family Rutaceae II. Systematic position of Rutaceae Different taxonomists have classified the family differently. Some of the prominent ones are as follows: Bentham and Hooker ( ) - the two British botanists, placed Rutaceae in: Class - Dicotyledons Subclass - Polypetalae Series - Disciflorae Order - Geraniales Arthur Cronquist (1988) - An American taxonomist, placed the family Rutaceae in: Division - Magnoliophyta Class - Magnoliopsida Sub-class - Rosidae Order - Sapindales Armen Takhtajan (1997)- a Russian taxonomist placed the family in the: Division - Magnoliophyta ( Angiospermae) Class - Magnoliopsida Sub-class - Rosidae Super-order - Rutanae Order - Rutales Rolf Dahlgren (1989) a Danish botanist, placed the family

7 in: Class - Magnoliopsida Sub-class - Magnoliidae Super-order - Rutiflorae Order - Rutales Robert Thorne (2003) an American taxonomist, placed the family in: Class - Angiospermae (Annonopsida) Sub-class - Dicotyledonae (Annonidae) Super-order - Rutiflorae Order - Rutales Angiosperm Phylogeny Group (2003) - a large collaborative group of taxonomists led by Peter Stevens placed the family in APG II as follows: Group-Eurosids II, Order Sapindales III. Phylogeny of Rutaceae: The family Rutaceae depicts a strong relationship with Simaroubaceae, Meliaceae,and Sapindaceae; all the four being thus, placed together in the order Sapindales. Morphological synapomorphies of the order include exstipulate, compound leaves, and a well-developed nectary disk. The secondary metabolites in both Meliaceae and Simaroubaceae are bitter tri-terpenoid compounds, which they share with Rutaceae. However, these two families differ from Rutaceae in lacking glandular-punctate leaves, and having

8 secretory cavities containing aromatic ethereal oils scattered in almost all organs. Molecular or phylogenetic analysis of both rbcl and atpb sequences from genera representing all sub-families and tribes generally recognized in Rutaceae showed this family to be paraphyletic, with none of the sub-families containing more than two genera being monophyletic. The analysis further showed the genera Spathelia and Dictyoloma (Rutaceae), Harrisonia (Simaroubaceae), Cneorum (Cneoraceae), and Ptaeroxylon (Ptaeroxylaceae) forming a clade sister to all other Rutaceae. This molecular study recommends the circumscription of all these taxa in Rutaceae. This sequence data analysis strongly indicates that Simaroubaceae and Meliaceae are the out-groups closest to Rutaceae. IV. Division of Rutaceae Engler (1931) divided the family into five sub-families mainly on the basis of morphological characteristics, such as degree of connation and number of carpels, fruit characteristics, (e.g. dehiscent vs. indehiscent, fleshy or dry, winged or not), and histology of the glands with ethereal aromatic oil. These subfamilies are: 1. Rutoideae: Carpels usually 4-5, often only united by styles, loculicidal dehiscence of fruit usually with the separation of endocarp. This is again divided into five tribes: Zanthoxyleae, Ruteae, Boronieae, Diosmeae, and Cusparieae. Examples: Zanthoxylum, Ruta, Correa, Diosma, and Cusparia. 2. Dictyolomatoideae: Carpels with several ovules, united at the base; fruit with separating endocarp. Example: Dictyoloma. 3. Spathelioideae: Carpels three, syncarpous, each carpel

9 with 2 pendulous ovules; fruit drupe and winged. Example: Spathelia. 4. Toddalioideae: Carpels 5-2 or 1, each with 2-1 ovules; fruit drupe or dry winged. Examples: Toddalia, Ptelea, Skimmia. 5. Aurantioideae: Fruit berry often with periderm and with pulp derived from sappy emergences of carpel wall. Examples: Aegle, Citrus, Limonia, Feronia. Recent analyses using molecular, chromosomal, and phytochemical evidences have, however, shown Aurantioideae as a monophyletic group, but not Rutoideae, Toddalioideae and others; and, therefore, a re-circumscription of these groups is recommended. V. Diversity in Rutaceae: A large family, comprising 162 genera and 1900 species (wild and cultivated), distributed widely in the tropical and sub-tropical regions of the world, especially abundant in Australia and South Africa. Zanthoxylum (200 species), Agathosma (180 species), Citrus (65 species) and Ruta (60 species) are some of the larger genera. About 23 genera with 70 species are found in India with common examples as species Citrus, Aegle, Murraya, Feronia, Atlantia, etc. VI. Economic importance of Rutaceae: The family is of great economic importance for its fruits, ornamental plants, timber, condiments, medicinal plants, oils, etc. a. Fruits: The family includes some of the world s most important, tasty and juicy citrus fruits, which are the richest source of vitamin C. They have good keeping and shipping qualities and are extensively grown in warmer countries. The better known species are: Citrus sinensis (Sweet orange, Malta): It is the most valued

10 commercial citrus of the world. The fruit is sweet, juicy and nutritious and highly esteemed as dessert fruit. Citrus reticulata (Orange, Santra): It is the most valued commercial orange of India and is mainly used as dessert fruit. Citrus limon (Lemon): It is widely used in the preparation of lemonade, squash and cooling beverages. It is also pickled. Citrus aurantifolia (Lime): It is used for culinary purposes and for flavouring jams, jellies, marmalades and alcoholic drinks. Citrus medica (Citron): The fruit is mainly used for pickles. The peel and pulp are made into marmalades and other preservatives. Citrus aurantium (Bitter orange): The fruit is used in the preparation of confections, marmalades, liquors and other drinks. Some other famous fruits of the family include Aegle marmelos (Bael, Bilva): The large globose fruit is famous for its edible aromatic pulp, which is also made into a drink. Feronia limonia (Wood apple or Elephant apple): The pulp of ripe fruits is eaten and is also made into sherbat and chutney. b. Condiments: Several Indian species of this family are used as condiments Zanthoxylum alatum (Tejpat): The bark is a famous condiment and is also used to clean teeth and as a carminative and stomachic. Zanthoxylum limonella: Leaves are used as condiment and the fruits are appetizing and digestive. Zanthoxylum nitidum: Fruits are used as condiment. Evodia lunuranthenoai: Leaves are used as condiment.

11 Murraya koenigii: Leaves are mixed with little turmeric to make curry powder, especially in India. c. Medicinal value: Several species are medicinally important such as: Pilocarpus: The source of pilocarpine, a drug used to treat glaucoma. Acranychia laurifolia: A poultice of the bark is applied on sores and ulcers. Aegle marmelos: Fruit pulp is a mild laxative whereas its roasted fruits are used against diarrhoea and dysentery and its root and stem bark in intermittent fever. Atalantia monophylla: The oil from fruits is used in paralysis and rheumatism. Barosma betulina: Leaves are used in curing kidney diseases. Cusparia febrifuga: Bark is used in the treatment of malaria. Zanthoxylum alatum: Seeds are used in cholera. The plant is insect-repellant. Zanthoxylum nitidum: Roots are used in toothache. Murraya koenigii: Bark and roots are used in intestinal disorders. Peganum harmala: Seeds are given in asthma, neuralgia and rheumatism. d. Ornamental plants: The family Rutaceae also presents many ornamental plants. Some of them are Murraya paniculata (Orange Jasmine): Commonly grown for its glossy green foliage and large clusters of fragrant white flowers. Ruta graveolens (Common Rue): Grown as an undershrub for fragrance and yellow flowers. The plant is narcotic and stimulant. Glycosmis pentaphylla: Grown for its glossy dark foliage and white or pinkish berries.

12 Skimmia arborescens: Grown usually for its handsome foliage and bright red berries. Dictamnus albus: Grown for its strong fragrance. Poncirus trifoliata: Excellent hedge for difficult areas of the landscape. Also grown as a specimen and often used as a hardy rootstock for oranges and other citrus cultivars. e. Timber: The wood obtained from Chloroxylon swietennia, Feronia limonia, Glycosmis pentaphylla, Murraya paniculata, Zanthoxylum alatum is used for veneering, making walking sticks, agricultural implements, etc. f. Oils: Plants of the family Rutaceae are an important source of essential oils. Leaves and fruit rind of various species of Citrus, Feronia, Murraya, Zanthoxylum, etc., are used in medicine and perfumery. Citrus bergamia: Seeds are the source of famous bergamot oil. Citrus sinensis: the essential oil obtained from the flowers (Neroli oil) and leaves and young shoots (Petilgrain oil) is used in the preparation of essences and perfumes.