Rubiaceae Week: February 6 to 12, 2012-Introduction: Rubiaceae Madder family, Coffee family or Bedstraw family named after madder genus Rubia Worldwide in distribution, but mainly distributed in the tropics and subtropics, especially the woody members. Genera nearly 630, species 13000 Major Genera Psychotria (1450 species) Galium (410) Ixora (370) Pavetta (360) Hedyotis (360) Tarenia (350) Randia (240) Gardenia (240) Mussaenda (190). Trees (Adina, Neolamarckia) or shrubs (Ixora, Gardenia), rarely herbs (Galium), sometimes climbing (Rubia) with hooked hairs, rarely epiphytic (Myrmecodia) with large swellings on roots inhabiting ants, usually with Iridoids, raphide crystals common. Leaves opposite, with interpetiolar stipules which often become as large a leaves and thus forming whorled arrangement of leaves, simple, entire, often turning blackish when dry, with colleters in leaf axils. Inflorescence cymose, sometimes capitate (Adina), or solitary (Gardenia). Flowers bisexual, actinomorphic, rarely zygomorphic (Posoqueria) epigynous, sometimes dimorphic (Randia). Calyx with 4-5 sepals, adnate to ovary, 5-lobed, lobes often very small, one sometimes enlarged and brightly coloured (Mussaenda). Corolla with 4-5 petals, (rarely 8-10), united, tubular, rotate or funnel-shaped, valvate, imbricate or twisted. Androecium with 4-5 stamens, free, epipetalous, anthers bithecous, dehiscence longitudinal, introrse, pollen grains usually tricolporate. Gynoecium with 2 (rarely 1-many) united carpels, ovary inferior, rarely superior (Pugama) or semi-inferior (Synaptantha), bilocular (rarely 1-many locules) with 1-many ovules in each chamber, placentation axile (rarely apical or basal), nectar disc usually present above the ovary, style slender, stigma capitate or lobed. Fruit a berry, capsule, drupe or schizocarp; seeds 1-many, with small embryo, curved or straight, endosperm present or absent. Economic importance: The family is economically important for being the source of coffee, quinine and a large number of ornamentals. Coffee is obtained from roasted seeds of Coffea arabica and C. canephora. Quinine, a remedy for malaria is derived from several species of Cinchona. Madder (Rubia tinctoria) was formerly cultivated for its red dye alizarin. Important ornamentals include Gardenia, Ixora, Hamelia, Neolamarckia (cadamb tree) and Mussaenda. Very clear concise description of the family Rubiaceae. As said above Latin word Ruber means red. The name of the family comes from the genus Rubia (Madder) Red dye is obtained from the roots of it. Attaching a link of my blog written 3 years back. FAMILY OF THE WEEK: RUBIACEAE Rubiaceae is a large family. In India there are about 76 genera and 274 species occurring chiefly in the tropical and subtropical Eastern Himalayas extending up to 4600 meters and mountains of southern and Western India. Vegetative characters: The habit is chiefly woody and the family consists of mostly trees and shrubs. The leaves are opposite decussate or sometimes whorled, simple entire and stipulate. The stipules show much variation in the form. They are frequently interpetiolar or intra petiolar. The stipules are often united. Sometimes as in Gardenia the four stipules are united into a conical cap which is thrown off as the bud opens. The bases of stipules are often glandular. Inflorescence and flowers: The inflorescence is basically a dichasial cyme and sometimes the small flowered cymes are aggregated into dense head as in Anthocephalus and Adina. In Morinda even the ovaries of the flowers in the head become fused. Rarely the flowers are solitary as in Gardenia and in Coffee one to three flowers stand in the axil of a leaf. The flowers are actinomorphic or rarely slightly zygomorphic, bisexual tetra or pentamerous and epigynous. The calyx is four or five lobed and the lobes are valvate. Sometimes as in Mussaenda one of the sepals in one or more flowers of an inflorescence becomes brightly coloured. The corolla is four or five fused petals and is salverform, rotate or funneliform. The petal lobes are valvate, twisted or imbricate in bud. The stamens are as many as the number of petals and they alternate with them. The anthers are dithecous introrse and opening lengthwise. The gynoecium is usually bicarpellary and syncarpous. The ovary is inferior and bilocular with axile placentation. The style is simple and the stigma is capitates or bilobed. Fruits and the seeds: The fruit is usually a septicidal or loculicidal capsule. Sometimes it is a berry(Coffee) or schizocarpic, separating into one seeded segments (Galium) Pollination and dispersal: The pollination is brought about by insects. Sticky fruits and persistent calyx limbs often favour their distribution by birds and animals. Sometimes the seeds are winged and are dispersed by wind. Examples: Coffee Cinchona Ixora coccinea Gardenia Mussaenda Anthocaphalus cadamba (Kadamb) Mitragyna parviflora (Kalam, Laghukadamb ) Adina cordifolia Randia spinosa Morinda Pavetta crassicaulis |
|
|