In this article we will discuss about:- 1. Characters of Gentianaceae 2. Distribution of Gentianaceae 3. Economic Importance 4. Affinities 5. Important Types.
Characters of Gentianaceae:
Plants herbs or sub-shrubs, branching dichotomous, leaves opposite, decussate, exstipulate; monochasial or dichasial cyme; flower actinomorphic hermaphrodite, hypogynous; calyx and corolla 4-5, fused, stamens 4-5, epipetalous; bicarpellary, syncarpous, superior, unilocular, parietal placentation, style simple; fruit capsule.
A. Vegetative characters:
Habit:
Generally annual or perennial herbs more or less bitter, glabrous, rarely shrubs.
Root:
Tap, branched.
Stem:
Green, soft, erect, herbaceous, dichotomously branched or modified into rhizome by which the plant perennates.
Leaf:
Opposite decussate rarely alternate, (Menyanthes) simple, entire, sessile, exstipulate, sometime radical.
B. Floral characters:
Inflorescence:
Cymose often dichasial.
Flower:
Actinomorphic (except in Conscora) hermaphrodite, hypogynous, bracteate or ebracteate, complete 4-5 merous.
Calyx:
Sepals 4-5, polysepalous or gamosepalous, tubular or deeply lobed, persistent, imbricate.
Corolla:
Petals 4-5, gamopetalous, rotate (Blackstonia) or funnel-shaped (Erythraea) or bell-shaped, twisted in bud.
Androecium:
Stamens 4-5, except in Conscora, alternating with corolla lobes, inserted in the tube or near the base of the corolla, anthers 2-celled, dorsifixed, basifixed or versatile, filaments slender, anthers dehisce by longitudinal slits or apical pores.
Gynoecium:
Garpels 2, syncarpous, generally median, ovary superior, or half inferior (Villarsia), usually 1-celled, placentation parietal, ovules many; style simple, linear; stigma terminal, usually 2-lobed, nectar-secreting disc at the base of ovary.
Fruit:
Capsule, dehiscent opening by two valves.
Seed:
Endospermic, small.
Pollination:
Entomophilous.
Floral formula:
Distribution of Gentianaceae:
Gentianaceae or Gentian family comprises 80 genera snd 900 species of world-wide distribution and most abundant in temperate and tropical regions.
Economic Importance of Gentianaceae:
1. Medicinal:
Gentiana lutea is the source of Gentian root tonic. The leaves of Swertia chirata being used as stomatichic. Chirona baccifera (South Africa) is a purgative.
2. Ornamental:
Exacum, Gentiana, Sabatia, Nymphoides are grown as ornamentals.
Affinities of Gentianaceae:
Gentianaceae is allied to Loganiaceae. Hutchinson (1926) has removed it from Loganiales and placed it under Gentianales near Primulales. Affinity with Caryophyllaceae has been established by the same author on account of similar nature of inflorescence and branching.
Gentianaceae is related to the Caryophyllaceae in having cymose inflorescence and dichotomous branching. It also bears relationship with the Apocynaceae and Loganiaceae, but differs from them by the absence of latex, presence of completely united carpels and parietal placentation.
Common plants of the family:
1. Conscora grandiflora – a branched herb.
2. Limnanthemum cristatum – Snow flake – a floating herb, very common in tanks.
3. Gentiana lutea – Gentian, a small branched herb.
4. Swertia chirata – Chireta – medicinal, chireta is obtained from its roots and stems.
5. Exacum tetragonum – common in north India in grassy places.
Division of the family and chief genera:
The family is divided into two subfamilies on the basis of phyllotaxy and aestivation of corolla lobes:
Sub-family I. Gentianoideae:
Leaves opposite. Corolla lobes twisted in bud. Vascular bundles bicollateral, i.e. intraxylary phloem is present e.g. Gentiana.
Sub-family II. Menyanthoideae:
Leaves alternate. Corolla lobes induplicate valvate. Vascular bundles collateral e.g. Menyanthes, Nymphoides.
Important Type of Gentianaceae:
Conscora grandiflora:
A branched herb; bracts perfoliate, common throughout India. Stem erect, 15-45 cm. 4-sided; leaves opposite, sessile, amplexicaul, oblong-lanceolate; flowers irregular, white; stamens 4, one perfect, others small imperfect, filaments short; ovary 1-celled; capsule oblong.