In this article we will discuss about:- 1. Characters of Boraginaceae 2. Distribution of Boraginaceae 3. Economic Importance 4. Affinities 5. Important Type.
Characters of Boraginaceae:
Plants mostly hispid herbs rarely shrubs or trees; leaves alternate, simple, usually entire; flowers hypogynous, actinomorphic, hermaphrodite; corolla gamopetalous; stamens epipetalous; gynoecium bicarpellary, syncarpous, 2 to 4 loculed due to the formation of a false septum; style gynobasic; seeds non-endospermic.
A. Vegetative characters:
Habit:
Predominantly herbs, mostly annuals (Heliotropium, Arnebia), a few shrubs and trees (Cordia); usually covered with dense hair; xerophytic.
Root:
A much branched tap root system.
Stem:
Erect, aerial, cylindrical, solid, branched, hispid, herbaceous, or woody in arboreal forms.
Leaves:
Cauline, ramal, simple, exstipulate, petiolate, alternate rarely opposite, usually converged with hairs.
B. Floral characters:
Inflorescence:
Solitary axillary; dichotomous corymb, uniparous scorpioid, with marked dorsiventrality, uncoiling as flowers open.
Flower:
Bracteate or ebracteate, pedicellate or sessile, complete, actinomorphic, rarely zygomorphic, hermaphrodite, hypogynous, pentamerous, polygamous in Cordia.
Calyx:
Sepals 5, rarely 4 to 8 lobed (Cordia); gamosepalous or free, imbricate or valvate, usually hairy, campanulate or tubular, persistent, green, inferior.
Corolla:
Petals 5, rarely 4 to 8 lobed, gamopetalous, campanulate, tubular or funnel-shaped, imbricate or valvate, inferior.
Corona:
Small scale-like or hair-like appendages arise from the throat of corolla tube.
Androecium:
Stamens 5, 4 to 8 in Cordia, epipetalous, filaments usually short, anthers dithecous, usually conical or sagittate, introrse.
Gynoecium:
Bicarpellary, syncarpous, ovary superior, bilocular, two ovules in each loculus, axile placentation; sometimes ovary becomes tetralocular due to the formation of a false septum so that there is one ovule in each loculus; style simple or 2-4 fid, hairy, terminal or inserted between the lobes (gynobasic); stigma distinct usually capitate, annular or lobed nectar secreting disc below the ovary.
Fruit:
A drupe, fruit has 4 nutlets, carcerulus (Heliotropium).
Seed:
Non-endospermic or endospermic.
Pollination:
Entomophilous.
Floral formula:
Distribution of Boraginaceae:
Boraginaceae is commonly known as the Forget me-not family. It includes about 100 genera and 2000 species widely distributed throughout temperature, tropical regions and more abundant in Mediterranean region.
Economic Importance of Boraginaceae:
The family is of little importance economically.
1. Food:
Fruits of Cordia dichotoma are used in pickles and jams and those of Ehretia serrata are edible.
2. Medicinal:
Alkanna tinctoria and Cordia are medicinal. Trichodesma indicum is diuretic. Symphytum is known to stimulate joining of fractured bones.
3. Ornamental:
Mertensia, Myosotis, Cordia, Cynoglossum are cultivated for ornamentals.
Primitive characters:
1. Trees and shrubs.
2. Leaves are simple and alternate.
3. Flowers are solitary axillary in some genera.
4. Flowers hermaphrodite, hypogynous, actinomorphic.
5. Stamens dithecous.
6. Seeds endospermic in some genera.
7. Pollination by insects.
Advanced characters:
1. Plants predominantly herbaceous.
2. Leaves exstipulate.
3. Flowers small and in distinct inflorescence.
4. The number of sepals and petals is mostly fixed i.e. five.
5. Corolla gamopetalous.
6. Corolla coronate.
7. Stamens five and epipetalous.
8. Gynoecium bicarpellary and syncarpous.
9. Fruit simple.
10. Seeds mostly non-endospermic.
Affinities of Boraginaceae:
The family has been placed under the Polemoniales together with the Convolvulaceae and Solanaceae by Bentham and Hooker while Engler palced it under the Tubiflorae. Hallier rejected the view and placed it as a primitive component of the Campanulales. He was of the opinion that the family arose directly from the Annonaceae or form stocks ancestral to the latter.
The family bears a close relationship with the Polemoniaceae on the one hand and with the Hydrophyllaceae on the other. It is also related to Lamiaceae and Verbenaceae. It resembles Solanaceae due to the presence of alternate leaves and regular flowers.
Common plants of the family:
1. Arnebia hispidissima:
A prostrate annual herb flowering from November to April.
2. Borago officinalis:
To which the family owes its name.
3. Cordia dichotoma (H. Lasura):
A small tree with mucilaginous fruits.
4. Ehretia acuminate:
Tree with numerous white fragrant flowers.
5. Heliotropium indicum (H. Unth chara):
A common weed.
6. Myosotis arvensis (Forget me not):
A herb with bright blue flowers with yellow centre.
7. Nonnea pulla:
Much branched hairy herb, common near railway lines and waste places.
8. Trichodesma indicum:
Annual herb with pale blue flowers; common throughout India.
Division of the family and chief genera:
The family is divided into 2 sub-families and 5 tribes:
Sub-family 1. Heliotropioideae:
Style terminal, fruit drupe; Heliotropium.
Sub-family 2. Boraginoideae:
Style gynobasic and fruit achenes.
Tribe (i). Cynoglosseae:
Flowers regular, base of the style more or less conical, tips of achenes not projecting above point of attachment. Cynoglossum.
Tribe (ii). Eritichieae:
Flowers regular, tips of achenes projecting above point of attachment. Eritrichium.
Tribe (iii). Anchuseae:
Flowers regular; base of style flat or slightly convex, achenes with concave attachment surface. Borago, Anchusa.
Tribe (iv). Lithospermeae:
Flowers regular, achenes with flat surface of attachment. Myosotis, Arnebia.
Tribe (v). Echieae:
Flowers zygomorphic. Echium.
Important Type of Boraginaceae:
Heliotropium strigosum (Fig. 76.1):
Habit:
An annual weed.
Root:
Tap, branched and deep root system.
Stem:
Aerial, erect, herbaceous, cylindrical, solid, branched, hispid.
Leaves:
Alternate, simple, petiolate, ovate, wavy, acute, covered with hair, unicostate reticulate.
Inflorescence:
Terminal two ranked spikes with marked dorsiventrality, uncoiling as the flowers open, uniparous scorpoid.
Flower:
Bracteate, pedicellate, complete, actinomorphic, hermaphrodite, pentamerous, hypogynous.
Calyx:
Sepals 5, gamosepalous, green, persistent, valvate, inferior.
Corolla:
Petals 5, gamopetalous, funnel-shaped, white, imbricate, inferior.
Corona:
5 projecting scales at its throat which alternate with stamen.
Androecium:
Stamens 5, epipetalous, alternipetalous, filaments short, anthers conical, basifixed, forming a cone around stigma, dithecous, introrse.
Gynoecium:
Bicarpellary, syncarpous, superior, bilocular becoming tetralocular due to the formation of false septum, one ovule per loculus, ovary hairy, axile placentation, style, simple, hairy, terminal, stigma capitate.
Fruit:
Four nutlets, carcerulus.
Seed:
Non-endospermic.
Floral formula:
