In this article we will discuss about the:- 1. Characters of Bignoniaceae 2. Distribution of Bignoniaceae 3. Economic Importance 4. Affinities.
Characters of Bignoniaceae:
Plant predominently lianous, compound leaves, zygomorphic flowers, anthers connivent in pairs; numberous ovule, silique-like woody capsule, large winged seed and non-endospermic.
A. Vegetative characters:
Habit:
Mostly trees or shrubs; often climbing or twining vine, rarely herbs.
Root:
Tap, deep, branched.
Stem:
Hard, woody and branched; weak in climbers and twiners, rootlet or tendril climbers.
Leaf:
Usually pinnately compound, opposite, decussate, rarely simple or alternate, exstipulate, terminal leaflet modified into tendril, adhesive disc or hook.
B. Floral characters:
Inflorescence:
Usually dichasial cyme with bracts and bracteoles.
Flower:
Bracteate, bracteolate, hermaphrodite, hypogynous, zygomophic, complete.
Calyx:
Sepals 5, gamopetalous, lobed or bilabiate, valvate.
Corolla:
Petals 5, obliquely campanulate or infundibuliform, imbricate, gamopetalous, lobes or teeth 5, sometimes bilabiate.
Androecium:
Stamens 4, didynamous, epipetalous, posterior staminode, sometimes 2 (Catalpa); anther two-lobed, lobes divaricate, disc present.
Gynoecium:
Carpels 2, syncarpous; ovary superior, bilocular with axile placentation, each loculus many – ovuled; sometime unilocular (Eccremocarpus) with two bifid parietal placentae; style terminal and single; stigma bifid.
Fruit:
Capsule – two valved septicidal or loculicidal or berry.
Seed:
Non-endospermic, flattened, winged.
Pollination:
Entomophilous.
Floral formula:
Distribution of Bignoniaceae:
Bignoniaceae or Bignonia family is primarily tropical or subtropical family comprising 120 genera and 800 species of trees or shrubs, often climbing or twining vines and rarely herbs.
Economic Importance of Bignoniaceae:
1. Timber:
Catalpa bignonioides, Millingtonia, Spathodea companulata, Tabebuia pentaphylla, Oroxylum are prized for timber.
2. Dye:
The leaves of Cybistax antisyphilitica are used as source of blue dye.
3. Ornamental:
The garden ornamental plants are represented by Pyrostegia venusa (Syn. Bignonia uenusta), Spathodea campanulata, Tecoma stans.
Affinities of Bignoniaceae:
Bignoniaceae is allied to Acanthaceae, Pedaliaceae and Scrophulariaceae. Wettstein considered the family a little advanced over Scrophulariaceae. Bessey placed the family in Scrophulariales, the origin of which was traced from Polemoniales (Boraginales).
Hallier included it in the Tubiflorae and placed it near Pedaliaceae and Acanthaceae to which it is also very allied. Hutchinson (1959) put the family under his 59th order Bignoniales which also includes family Pedaliaceae; according to him the origin of Bignoniales was from Loganiales.
Common plants of the family:
1. Crescentia cujete – Calabash-fruit large, ground-like.
2. Jacaranda acutifolius – Jack tree a road-side avenue tree with wonderful masses of purplish flowers.
3. Catalpa speciosa – tree grown for valuable wood.
4. Bignonia vensusta – Climber, ornamental plant.
5. Millingtonia hortensis – Indian cork – tree.
6. Tecoma stans – garden shrub.
7. Tabebuia – West Indian Box tree.
Division of the family and chief genera:
According to Schumann the Bignoniaceae is separated into four tribes:
Tribe I. Bignonieae:
Ovary completely bilocular, compressed, parallel to the septum or ovary may be cylindrical. Capsule septifragal. Seeds winged. Mostly climbing shrubs by means of leaf tendrils or sometimes trees. Genera: Glaziovia, Bignonia, Oroxylum, Millingtonia etc.
Tribe II. Tecomeae:
Ovary bilocular compressed, at right angles to the septum, or ovary may be cylindrical. Capsule loculicidal with winged seeds. Erect shrubs or trees, rarely climbers by tendrils. Genera: Tecoma, Catalpha, Spathodea, Heterophragma, Pajanelia etc.
Tribe III. Eccremocarpeae:
Ovary unilocular. Capsule dehiscing from base upwards. Seeds winged. Climbing shrubs by tendrils. Only genus Eccremocarpus (Peru, S. America).
Tribe IV. Crescentieae:
Ovary uni- or bilocular. Fruit berry or dry indehiscent. Seeds not winged. Erect trees or shrubs. Genera: Kigelia, Crescentia etc.