In this article we will discuss about:- 1. Characters of Brassicaceae 2. Distribution of Brassicaceae 3. Economic Importance 4. Affinities 5. Important Types.
Characters of Brassicaceae:
Flowers actinomorphic rarely zygomorphic, hermaphrodite; sepals four in two whorls of two each, petals four, diagonally arranged-cruciform; stamens six, tetradynamous; gynoecium bicarpellary, syncarpous, parietal placentation, bilocular due to the formation of flase septum (replum); fruit siliqua or silicula.
A. Vegetative characters:
Habit:
Generally herbs, annual (Brassica, Capsella) or biennial or shrubs. Common Indian herbs are Eruca, Alyssum, Nasturtium, Lepidium, Coronopus etc. Vegetative reproduction is by bulbils (Dentaria bulbifera) or by coral roots.
Roots:
Tap root, swollen on account of stored food materials. It may be conical (Radish), fusiform or napiform (Turnip).
Stem:
Herbaceous, erect, cylindrical (Iberis, Brassica) rarely woody or some times reduced (Raphanus & Brassica species), glabrous or hairy, solid and branched.
Leaves:
Alternate or sub-opposite, simple, exstipulate (Brassica campestris). May be cauline or radical (Raphanus), generally sessile, hairy, entire and with unicostate reticulate venation.
B. Floral characters:
Inflorescence:
Raceme (Brassica campestris) corymbose raceme (Iberis) or corymb.
Flower:
Pedicellate, ebracteate, hermaphrodite, actinomorphic rarely zygomorphic (Iberis and Teesdalia), hypogynous, complete or incomplete (Lepidium) and tetramerous.
Calyx:
Sepals 4 arranged in two whorls of two each, polysepalous (2 antero-posterior and 2 lateral), 2 lateral sepals may be saccate, imbricate aestivation, inferior.
Corolla:
Petals 4, alternate with sepals, polypetalous, petals arranged in the form of across known as cruciform. This arrangement is characteristic of the family Petals usually clawed, petals generally equal rarely unequal (Iberis, Teesdalia) or sometimes petals may be replaced by stamens (Capsella bursa pastoris).
Androecium:
Stamens 6, arranged in two whorls, outer two stamens short and inner four long (2+4), tetradynamous, polyandrous, anthers dithecous basifixed, introrse. Disc like nectaries, variable in number, present at the base of stamens. In some cases the number of stamens is variable – 16 (Megacarpaea), 4 (Cardamine hirsuta), 2 (Coronopus) etc.
Gynoecium:
Bicarpellary rarely tricarpellary (Lepidium sativum), syncarpous, ovary superior, unilocular, becomes bilocular due to the development of false septum called replum: parietal placentation, ovules many, style short, stigma simple or bifid. The crucifer carpel has been a puzzling subject for the morphologists and their attention attracted towards its for a long time. According to some there are only two carpels while others hold that there are four carpels.
Fruit:
Siliqua or silicula, sometimes lomentum (Raphanus); when the valves separate in a siliqua the seeds remain attached to the replum.
Seed:
Ex-albuminous. The germination of seed is epigeal.
Pollination:
Self or cross pollinated; flowers are visited by insects due to the presence of nectaries. Cleistogamy is found in Cardamine chenopodifolia. Anemophilous pollination is found in Pringlea.
Floral formula:
Distribution of Brassicaceae:
This family is also called Brassica family. The family includes 375 genera and 3200 species according to Willis. It is distributed all over the world but mainly confined to the Mediterranean region and north temperature regions.
Economic Importance of Brassicaceae:
This family is of considerable economic importance.
1. Food:
The plants of this family which are cultivated as vegetable crops are:
Brassica oleracea var. botrytis (H. Phul gobhi), B. oleracea var. capitata (H. Band gobhi), B. oleracea var. caulorapa (H. Gand-gobhi), Brassica campestris var. sarson (white mustard), Brassica rapa (H. Shalgam), Raphanus satiuus (H. Muli), are edible and cooked as vegetables.
2. Oil:
The seed of B. campestris (or white mustard) yield mustard oil or Karwa-tel which is widely used as a cooking medium. B. nigra (H. Kalirai) and B. juncea (H. rai) also produce oil.
After extracting oil the cake is left behind which is highly nutritious as a cattle feed; the oil cake is also used as soil fertilizer. Raphanus seeds also produce a pungent oil which is often used in adulteration of sarson oil; this oil has digestive properties.
3. Medicines:
The leaves and tender shoots of Lepidium sativum are used in liver complaints, asthma, cough and bleeding piles. Rorippa montana is an appetizer and a stimulant. The seeds of Cheiranthus cheiri are used in bronchitis and fever. The flowers are used in paralysis and impotency. Lobularia is used for gonorrhoea. Iberis amara is used in rheumatism and gout.
4. Ornamentals:
Some plants are grown in gardens for their beautiful flowers viz. Cheiran thus cheiri (wall flower), Iberis amara (candituft) Lobularia, Matthiola (stock), Hesperis (rocket), Alyssum, Lunaria (honesty) etc.
Primitive characters:
1. Leaves simple and alternate.
2. Flowers hermaphrodite, hypogynous and actinomorphic.
3. Calyx and corolla free.
4. Stamens polyandrous.
5. Ovules anatropous.
Advanced characters:
1. Plants are generally herbs-annual or biennials.
2. Leaves exstipulate.
3. Flowers ebracteate and sometimes zygomorphic (Iberis).
4. Gynoecium bicarpellary and syncarpous.
5. Fruit simple.
Affinities of Brassicaceae:
Rendle placed this family under the order Rhoedales; Bentham-Hooker placed it under the cohort Parietales. The family is related to the Papaveraceae on one hand and to the Capparidaceae on the other. Bentham & Hooker and Hutchinson (1948, 1964) hold the view that Brassicaceae is derived from the Papaveraceous ancestors whereas Eames, Arber, Hayek and Puri believe it to have a Capparidaceous alliance.
The three families, Capparidaceae, Brassicaceae (Cruciferae) and Papaveraceae have in common the features of tetramerous perianth, bicarpellary syncarpous gynoecium and parietal placentation. These characters gave problematic issues as to whether the Brassicaceae (Cruciferae) originated from the Capparidaceae or descended from the Papaveraceae.
The anatomy and morphology of stamens and carpels of cruciferous flower bears testimony to a papaverous ancestory. But in Brassicaceae the stamens are tetradynamous and not in Papaveraceae.
Comparison of floral diagram indicates that Brassicaceae is closely allied to Capparidaceae. But in Brassicaceae gynophore and variable number of stamens are absent where as these are the prominent characters of Capparidean flowers.
Within the Rhoedales reduction seems to have taken place in the number of stamens. In the Papaveraceae there are numerous stamens but in its two subfamilies reduction has occurred. In the Hypecoideae there are only four stamens; in the Fumarioideae the stamens are arranged in two bundles each with one dithecous and two monothecous anthers.
In the Capparidaceae the number of stamens range between several (as in Capparis) to six (as in Gynandropsis). Finally in Cleome there are only four stamens. The floral diagram of Cleome spinosa with six stamens is remarkably similar to that of the Brassicaceae (Cruciferae).
In this family the general condition is tetradynamous but may be reduced to only two (as in Coronopus). Celakovasky considers the above view as most satisfactory.
Cronquist (1968) too considers that the Brassicaceae (Cruciferae) evolved from the Capparidaceae.
Common plants of the family:
1. Brassica campestris (Sarson) – a cultivated herb.
2. Iberis amara (Chandni) – annual, ornamental, herb cultivated in winter.
3. Cherianthus cheiri (Wall flower) – ornamental annual herb.
4. Rorippa monatna (Water cress) – semi wild.
5. Capsella bursa – pastoris (Shepherd’s purse) – common weed.
6. Farsetia jaquemontii – common weed.
7. Coronopus didymus (= Senebiera didyma) – wild in waste places.
8. Eruca sativa (Tara mira) – cultivated for seeds that yield an oil.
Division of the family and chief genera:
Linnaeus utilised the pod as the character for his classification.
He divided Tetradynamia into two orders:
Order 1. Siliculosae – fruit a silicula.
Order 2. Siliquosae – fruit a siliqua.
Prantl divided the family on the presence or absence of hairs into two series.
Series I. Hairs un-branched or hairs absent, never glandular:
This series includes two sub-families:
1. Thelypodieae:
With stigma developed equally all around, style undivided. Thelypodium, Pringlea.
2. Sinapeae:
With stigma better developed over placentae. Iberis, Brassica, Raphanus etc.
Series II. Hairs branched, sometimes glandular:
This series includes two sub-families:
1. Schizopetaleae:
With stigma equal all round. Physaria.
2. Hesparideae:
With stigma better developed above the placentae. Alyssum, Capsella, Cheiranthus etc.
O. E. Schulz (1936) divided the family into 19 tribes on the basis of a wide variety of characters.
Important Types of Brassicaceae:
1. Brassica campestris, Linn. (Fig. 31.1):
Habit and habitat:
An annual herb, cultivated for seeds which yield oil.
Root:
Tap and branched.
Stem:
Herbaceous erect, cylindrical, solid, glabrous or hairy.
Leaf:
Simple, alternate, exstipulate, lower ones lyrate and upper oblong or lanceolate, unicostate reticulate venation, hairy, sessile.
Inflorescence:
A corymbose-raceme.
Flower:
Ebracteate, pedicellate, complete, actinomorphic, hermaphrodite, cruciform, tetramerous, hypogynous, and yellow.
Calyx:
Sepals 4 (2 + 2) in two whorls, outer whorl antero-posterior, the two lateral one saccate, green, polysepalous, inferior.
Corolla:
Petals four, polypetalous, cruciform, valvate, inferior, yellow.
Androecium:
Stamens six, tetradynamous, in two whorls, the outer with two short lateral stamens and inner with four long stamens arranged in two median pairs. Basifixed, polyandrous, introrse. Four green nectaries are present, on the inner side of each short stamen and a similar one at the base but outside each pair of long median stamens, inferior.
Gynoecium:
Bicarpellary, syncarpous, superior, unilocular becoming bilocular by the development of false septum called – replum; parietal placentation, style short, stigma bilobed.
Fruit:
Siliqua.
Seed:
Non-endospermic.
Floral formula:
2. Iberis amara, Linn. (Fig. 31.2):
Habit and habitat:
Herbaceous annual, cultivated in the gardens.
Root:
Tap, branched and annual.
Stem:
Herbaceous, erect, branched, cylindrical, solid, green and glabrous.
Leaf:
Cauline, ramal, alternate, simple, exstipulate, sessile, glabrous, or hairy, unicostate reticulate venation.
Inflorescence:
Corymbose raceme.
Flower:
Ebracteate, pedicellate, complete, zygomorphic, zygomorphy is due to two longer anterior petals, tetramerous, hypogynous, white.
Calyx:
Sepals 4, polysepalous, in two whorls of two each, green, imbricate aestivation, inferior.
Corolla:
Petals 4, polypetalous, cruciform, petals unequal-2 posterior smaller and 2 anterior longer, valvate, white.
Androecium:
Stamens 6, polyandrous, arranged in two whorls; outer of 2 short stamens and inner of 4 longer stamens, tetradynamous, anthers basifixed and introrse.
Gynoecium:
Bicarpellary, syncarpous, ovary superior, unilocular but becomes bilocular due to the formation of false septum – the replum, parietal placentation; style short; stigma capitate.
Fruit:
A silicula.
Seed:
Non endospermic.
Floral formula:
3. Coronopus didymus, Linn. (Syn. Senebiera didyma) (Fig. 31.3):
Habit and habitat:
An annual, winter weed.
Root:
Tap, branched and annual.
Stem:
Prostrate, herbaceous, cylindrical, branched, solid, green and glabrous.
Leaf:
Alternate, exstipulate, sub-sessile or sessile, simple, pinnatifid, glabrous, unicostate reticulate venation.
Inflorescence:
A typical raceme.
Flower:
Pedicellate, bracteate, complete, hermaphrodite, actinomorphic, hypogynous, greenish white, small.
Calyx:
Sepals 4, polysepalous in two whorls of two each, antero-posterior sepals form the outer whorl, green, linear, inferior.
Corolla:
Petals 4 polypetalous, very small and scale-like, cruciform, whitish green, alternating with the sepals, valvate, inferior.
Androecium:
Stamens 2, anterio-posterior, polyandrous, small nectaries are present at the bases of stamens, anthers basifixed, dithecous, introrse.
Gynoecium:
Bicarpellary, syncarpous superior, unilocular becoming bilocular due to the formation of false septum, parietal placentation, 2 ovules per placentum, style small, stigma bifid.
Fruit:
A silicula.
Seed:
Non-endospermic
Floral formula:
