Classification of Rhoeadales: 4 Families

In this article we will discuss about the classification of Rhoeadales. According to Engler, Rhoeadales consists of four families:- 1. Papaveraceae 2. Capparidaceae 3. Cruciferae 4. Moringaceae.

Family # 1. Papaveraceae:

Papaveraceae are predominantly herbs with milky or coloured latex. Leaves are alternate, simple, entire or lobed, often much dissected, exstipulate; rarely crowded at base.

Flowers solitary or in racemes or cymes; bisexual, usually regular, hypogynous 2- or 3-merous. Sepals 2 or 3, free, caducous, imbricate. Petals 4 or 6 in 2 whorls, imbricate, crumpled in bud, deciduous. Stamens numerous, in more than one alternating whorl, 2-3 in each whorl or in multiples of 2 or 3; anthers bilocular, dehiscing longitudinally.

Carpels 2-many, syncarpous, forming a unilocular superior ovary; ovules many on parietal placentas which are usually protruding inside and often meeting at the centre so that the ovary becomes multilocular, sometimes falsely bildtular by a septum joining the 2 opposite placentas; stigmas as many as carpels, radiating from the centre and forming a lobed structure, persistent, Style present or not.

Fruit usually a capsule, opening by apical pores or valves, rarely fruit indehiscent. Seeds small, globose or somewhat kidney- shaped with oily endosperm and small embryo.

Although generally herbaceous a few are climbers or scandent shrubs, e.g. Adlumia, Dactylocapnos, etc. Hypecoum procumbens Linn, is a creeper. Bocconia arborea S. Wats, is a short tree. Leaves are simple, but Dactylocapnos and some Corydalis have compound or decompound leaves. In Chelidonium the small flowers are in umbels; in Macleya the inflorescence is paniculate.

In Eschscholtzia the 2 sepals are coherent and form a calyptra which falls off as the petals grow. In the subfamily Fumarioideae the flowers are trans­versely zygomorphic; one or both of the 2 petals of the outer whorl are saccate or spurred, the inner petals form a hood over the stamens. Outer stamens have bithecal anthers while the inner have monothecal anthers. In Bocconia and Macleya corolla is absent.

The ovary is unilocular or it is multilocular when the placentas meet in the centre. In Glaucium the ovary becomes 2-chambered due to the formation of a replum uniting the 2 opposite placentas. Platystemon has a partially syncarpous multilocular ovary of many carpels united laterally in the lower portion, the styles remaining free.

Bocconia has a unilocular ovary with a solitary basal ovule. Fruits are capsular and open by valves or pores near the apex or dehiscing longitudinally from apex downwards as in Glaucium or from base upwards as in Chelidonium.

In Hypecoum the pod like fruit deve­lops transverse septa between the seeds and breaks up into several one-seeded parts when ripe. The seeds are arillate in Bocconia. In some species of Corydalis the embryo germinates with one cotyledon only.

The flowers are insect-pollinated. In Hypecoum procumbens L. the inner surface of petals have pockets where the pollens fall when the stigmas are still immature. When an insect enters the flower the pockets open as the insect presses against them and dust the body of the insect with pollens. The flower is protandrous in this case but is protogynous in other cases. Self-pollination also sometimes occurs.

In this family the stomatal guard cells are usually not accompanied with subsi­diary cells. Vessels have simple perforations and simple pits in wood parenchyma. Latex tubes or vessels are present in almost all parts of the plant body; these are thin- walled, articulate and closed. The family with about 700 species in 35 genera is distributed in the temperate and sub-temperatc countries of the northern hemisphere.

It is subdivided into 3 sub-families as given below:

I. Papaveroideae:

Milky or coloured or watery latex present; leaves simple, entire or lobed; flowers regular; petals not spurred or saccate; stamens many, free, fruit capsular.

II. Hypecoideae:

Latex absent; leaves pinnately cut; flowers regular; the outer petals are trilobed, the inner tripartite; petals not saccate or spurred; stamens 4; fruit a lomentum.

III. Fumarioideae:

Latex absent but have oil-sacs;. leaves compound or much dissected; flowers zygomorphic; outer petals spurred or saccate; inner petals hooded; stamens 6, tripartite; fruit dehiscent or indehiscent.

The subfamily Fumarioideae has been raised to the rank of a distinct family by many authors and there is enough justification for that. Takhtajan raises the subfamily Hypecoideae also to the rank of a family but has not been supported by others in his treatment.

Floral formula may be expressed as:

Papaver somnifcrum Linn, is an important plant that yields opium which is the coagulated latex obtained by incision on the unripe capsule.

The seeds are the “Posta- dana” an article of food and also yield an oil when pressed. P. somniferum or the opium poppy is cultivated in India as well as in many other tropical countries. P. rhoeas Linn, is the garden poppy much cultivated for the large showy flowers and Eschckoltzia califomica Cham, is also cultivated for the same purpose.

Argemone mexicana Linn, is an obnoxious weed in all tropical countries. Blue poppies are the Meconopsis species of the Himalayas and China and are often cultivated. Dactylocapnos thalictrifoha Wall, and many species of Corydalis occur also in the Himalayas.

Papaveraceae is allied to Capparidaceae and Cruciferae to some extent having dime-­rous flowers, superior, unilocular, syncarpous ovary, ovules many on parietal placentas, etc.

The sessile stigmas and the projecting placentas resemble the family Nymphaeaceae to some extent and particularly the genus Platystemon with its trimerous flower and semi- free carpels resembles Cabomba of Nymphaeaceae (or Cabombaceae if treated as a distinct family). The genus Corydalis resembles the Monocotyledonae also to some extent having only one cotyledon functioning at the time of germination.

The characters of Fumariaceae when treated, as a separate family are given below in brief:

Herbs, climbers or scandent shrubs with repeatedly pinnate leaves; latex absent. Racemes subteneded by bracts. Flowers generally transversely zygomorphic. Sepals 2, caducous; petals 4 in 2 whorls, more or less connate, one or both of the outer whorl saccate or spurred, the inner petals hooded.

Stamens 6 in 2 series more or less coherent in 2 bundles; each stamen is branched into 3 near the upper end, the middle branch is bithecal and the lateral branches are monothecal; one bundle of the stamens has a spur projecting into the spur of the petal. Nectar glands often present at the base of the androecium.

Carpels 2; ovary syncarpous, unilocular superior; ovules 2-many on parietal placentas; stigma entire or bilobed on a slender style. Fruit a capsule, dehiscing transversely, or a nut. Seeds with a very small embryo and fleshy endosperm; cotyleledons 2 or 1.

Fumariaceae consists of about 425 species in 19 genera mostly in the tempera u, countries. Fumaria indica Pugsl. occurs in the plains of India. Dactylocapnos and Corydalis are found in the Himalayas.

Family # 2. Capparidaceae:

(Capparaceae)

Capparidaceae are herbs or shrubs, often scandent or climbing, rarely trees; lit ex absent. Leaves are alternate, simple or palmately compound, stipulate or exstipuate. Inflorescence race­mose, or flowers solitary; bracteate.

Flowers bisexual, hypogynous, actinomorphic or zygomorphic, usually tetramerous; androgynophore or gynophore usually present; lateral outgrowth of the axis also often seen in the form of swelling or disc or tubular structure below or above corolla.

Sepals 4, in 2 whorls, free or rarely more or less united, valvate or imbricate. Petals 4, rarely more, free, imbricate; rarely petals absent. Stamens numerous or 8 or 6 or only 4 and alternate to the petals, free, sometimes on an androphore; filaments long; often some stamens reduced to petaloid staminodes; sta­mens never tetradynamous.

Carpels 2, sometimes 4; ovary syncarpous, unilocular, usually on a gynophore; ovules many, campylotropous, on parietal placentation; style short or absent, stigma depressed or capitate. Fruit a siliqua, capsule, berry or samara, farely a nut.’ Seed kidney-shaped, exalbuminous; embryo large, variously folded.

Flowers are bisexual but unisexual’ flowers are produced in Podandrogyne. Actinomorphic flower is found in almost all genera but there are exceptions. The zygomorphy results due to unequal development of sepals and petals. In some species of Capparis the posterior sepals form a hood like structure.

In Pteropetalum the posterior petal is much larger than the anterior. ‘Sepals and petals are united in Ebiblingia where the calyx is 4-lobed and the petals are also united and the posterior petals form a large hood pro­tecting the stamens. In some genera petals are absent.

Anomalus secondary .thickening is observed in a few genera where the original cambium ring is replaced by new cambium rings that add secondary phloem and xylem. Some genera being xerophytic heavy cuticularisation of epidermis takes place having sunken stomata. Large amount of mechanical tissue and stone cells also developed. The plants have thorns or spines and small leaves and are provided with trichomes.

Floral formula is shown below:

The family contains about 700 species in 46 genera and is distributed in all tropical and subtropical countries; some are inhabiting the deserts of Africa and the steppes of Australia. In India it is represented by several species in the plains belonging to the genera Cleome, Polanisia, Gynandropsis, Capparis, Crataeva, etc.

Crataeva nurvala Buch. Ham is the Barun tree, the bark of which has antiseptic properties. The flower buds of Capparis spinosa L. are the “Capers” used in flavouring food. Cleome viscosa Linn, and Cleome gynandra Linn, have medicinal properties.

The family is closely related to Cruciferae having similar arrangement of floral parts. It is also related to Papaveraceae to some extent and is considered to be inter­mediate between these 2 families.

Most workers consider that Capparidaceae and Cruci­ferae came from the same ancestral stock or Cruciferae might have been derived from a primitive group of Capparidaceae. Hutchinson traces its affinity with Moringaceae for the presence of so many woody members and includes Capparidales in Lignosae while Cruciales is included in Herbaceae.

Capparidaceae is splitted by some into Cleomaceae and Capparidaceae.

Family # 3. Cruciferae:

(Brassicaceae)

Cruciferae are herbs with watery juice which is usually pungent. Leaves are radical or cauline, alternate, exstipulate, simple or pinnate, entire or variously lobed or cut. Flowers race­mose or corymbose, regular or the outer ones radiant. Sepals 4, free, imbricate, often saccate at base. Petals 4 free, hypogynous, spreading, usually placed crosswise, imbri­cate or convolute.

Disc-glands usually 4, sessile, opposite the sepals. Stamens 6, tetra- dynamous; 2 outer opposite the lateral sepals; 4 longer, usually in pairs and opposite the median sepals; rarely stamens 4 or only 2.

Ovary superior, of 2 lateral carpels, 1-locular or usually falsely 2-locular, the loculi separated by the replum connecting the two parietal placentas; the edges of the replum is placentiferous; rarely the ovary cell is divided by transverse partitions; ovules few or many, rarely 1 and basal, campylo­tropous or amphitropous.

Fruit usually 2-valved (siliqua), the valves breaking away from the replum, or indehiscent. Stigma generally commisural, i.e. placed immediately above the placentas. Seeds without endosperm, with- large cotyledons and folded embryo.

The commissure in the pistil is regarded by some as the true carpel bearing the placentae, so that the pistil consists of 2 pairs of carpels, a lateral barren pair and a median fertile pair. The lateral pair forms the valves of the fruit which separate at maturity and the median pair forms the replum.

Range of Floral Structure:

Plants of this family have regular flowers as a rule, but in Iberis and Teesdalia the flower becomes zygomorphic with 2 outer petals enlarged. Petals are sometimes absent or almost so in some species of Coronopus, Lepidium or Rorippa as well as in Capsella where the petals are sometimes modified into stamens.

Lateral stamens are generally absent in some Cardamine while in Lepidium and Coronopus only 2 median stamens are present. In Megacarpaea there are as many as 16 stamens.

Four or more carpels are found in Tetrapoma and Holargidium. Lepidium sativum Linn, has a tricarpellary ovary. Many genera produce abnormal flowers with ovaries com­posed of carpels more than 2 in number. Puri concludes that the present bilocular type of ovary with parietal placentation has resulted from a 4-loculed ancestral type with axile placentation.

Eames and Wilson (1930) hold that the modern Cruciferous ovary has been derived from 4 carpels, 2 fertile, ones in the inner whorl and 2 sterile ones representing an outer whorl and that the replum is formed by the fused walls of the 2 fertile carpels with their ovules now in the locules of the sterile carpels.

That the family is closely related to Papaveraceae and Capparidaceae there is little disagreement. It is placed along with 2 above families in the Rhoedales of Engler where are included Resedaceae and Moringaceae. The common characters are bisexual hypogynous flowers, typically cyclic perianth and androceium, syncarpous ovary, parietal placentation and usually capsular fruits.

Hutchinson following Bentham and Hooker states that the family has been derived from Papaveraceous ancestors. But other authers hold that the morphological characters of androecium and gynoecium and the anatomical character suggest its origin from Capparidaceous ancestors.

According to V. Puri Capparidaceae and Cruciferae both having apparently 2 carpelled ovary and parietal placentation, have been derived from an ancestral group having a quadrilocular ovary that was 4 carpelled and had axile pla­centation.

This is a large family with about 2500 species in 350 genera growing in the cooler parts of both hemispheres with their chief development in the northern hemisphere and especially in the Mediterranean region.

Pomel classified the family into 3 groups on the basis of cotyledons as noted below:

A. Platylobeae:

Cotyledons flat, radicle accumbent or incumbent.

B. Orthoploceae:

Cotyledons longitudinally folded, radicle in the channel formed by the cotyledons.

C. Pleuroploceae:

Cotyledons rolled or transversely folded.

The family includes a number of plants economically important. Seeds of Brassica nigra Goch; B. campestris Linn, B. juncea Czern. & Goss. etc. yield the Mustard oil. Brassica oleracea Linn. var. botrytis Linn, is the Cauliflower. B. oleracea Linn, var capitata Linn, is the Cabbage, B. oleracea Linn, var gongylod.es Linn, is the Kuolkhol and B. oleracea Linn, var gemmifera DC is the Brussels sprout.

Brassica rapa Linn is the Turnip and Raphaiuis sativus Linn, is the Radish. Many are cultivated as ornamental plants, viz.: Iberis (Candy-tuft), Matthiola (Stocks), Cheiranthus (Wall-flower), etc.

Family # 4. Moringaceae:

Moringaceae is a monotypic family of soft wooded trees with gummy juice; deciduous. Leaves are compound, simple pinnate or bi- or tripinnate, leaflets opposite, entire; stipules reduced to glands or absent; pulvinus distinct. Panicles cymose, axillary; flowers zygomorphic, hermaphrodite, perigynous. Sepals 5, imbricate, inserted on the margin of cupular hypanthodium.

Petals 5, free, unequal, inserted on the hypanthodium; the upper pair smaller than the lateral, the lowest (the anterior) largest. Stamens inserted on a disc, 10-12, free and declinate, 5 fertile alternating with 5-7 staminodes; filaments unequal in length, anthers of fertile stamens versatile, monothecal, dehiscing longitudinally.

Ovary peri- or hypogynous, of 3 carpels, syncarpous, unilocular, stipitate, often curved and hairy; ovules many, anatropous, biseriate on 3 parietal placentas; style slender, tubular with a truncate or club-shaped stigma. Fruit an elongated 3-valved capsule, 3-6-angled, corky and pitted inside; seeds many in the “depressions of the valves, winged or not, without endosperm and with oily cotyledons, embryo straight.

The single genus Moringa with 8 species occurs in Africa and Asia. M. oleifera Lam. is cultivated all over India in the plains and in other tropical countries for the fruits, flowers and young leaves which are used as vegetables. The seeds yield an oil which is used in lubricating fine machinery, e.g. watches, etc. The soft wood is used for fuel and is useless for any other purpose.

The family was placed in Rhoeadales by Engler because of its syncarpous ovary, many ovules on parietal placentation, capsular fruits and oily seeds. The monothecal anther and straight embryo are characters that speak against its inclusion in an order containing Papaveraceae.

The stipitate ovary has some resemblance to the gynophore of Capparidaceae where the flowers are often slightly irregular. Moringaceae is therefore placed in Capparidales (or Capparales) by Hutchinson, Takhtajan and Cronquist.