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In this article we will discuss about:- 1. Characters of Rosaceae 2. Distribution of Rosaceae 3. Economic Importance 4. Affinities 5. Important Types.
Characters of Rosaceae:
Shrubs with prickles; leaves simple or compound, pinnate, alternate, stipulate; flowers actinomorphic very rarely zygomorphic hypo-, peri- or epigynous; calyx gamosepalous, 5; petals 5, polypetalous; stamens indefinite; carpels 1 to many, apo- or syncarpous, situated on swollen receptacle; fruit a collection of achenes, drupe or pome.
A. Vegetative characters:
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Habit:
The plants show great variation in habit. The plants may be annual (Neurada spp.) or perennial prostrate herb, scandent or climbing or erect (Rosa spp.), shrubs or trees. Cydonia species are bushes. Trees are common and many of them are our popular fruit trees e.g. Prunus amygdalus (H. Badam); Prunus persica (H. Aru);Pyrus communis (H. Naspati); Pyrus mains (H. Seb) etc.
Root:
Tap, branched sometimes adventitious arising from stem cuttings.
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Stem:
Erect, prostrate or climber, branched, hard and woody, runner or sucker. Vegetative propagation takes place by means of runner or sucker or cuttings, many shrubby species are with spines, in some prickles are present (Rosa spp.).
Leaves:
Alternate rarely opposite (Rhodotypos), simple or compound sometimes pinnately compound, stipulate, stipule may be minute and caducous (Spiraea, Pyrus), adnate and persistent (Rosa, Rubus), leaf base conspicuous.
B. Floral characters:
Inflorescence:
Solitary (Potentilla, Rosa servica) or grouped in racemose (Agrimonia). terminal corymbose (Rosa moschata), terminal cyme (Geum) or corymbose cyme (Potentilla sibbaldi).
Flower:
Actinomorphic very rarely zygomorphic (Chrysobalanoideae), bisexual or rarely unisexual (Spiraea aruncus), pentamerous or tetramerous, hypogynous or epigynous (Pyrus) or perigynous (Rosa); stipules may be represented by epicalyx (Fragaria, Potentilla).
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Calyx:
Sepals 5, gamosepalous, adriate to the receptacle; sometimes epicalyx present; calyx tube remains free or adnate to the ovary, green, imbricate or valvate aestivation.
Corolla:
Petals 5, or multiples of 5, polypetalous, rosaceous, inserted on the receptacle cup variously coloured; petals entirely absent (Poterium, Alchemilla, Pygeum gardneria), or petals may be indefinite (Rosa spp.); sometimes stamens may be transformed into petal like structures; imbricate aestivation in bud.
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Androecium:
Stamens 2, 3 or 4 times the number of petals, may be indefinite, free, commonly borne on the rim of the torus; anthers small, dithecous, splitting longitudinally, introrse in bud; rarely stamens 1 to 4 (Alchemilla).
Gynoecium:
Carpel 1 (Prunus, Prinsepia) or (Agrimonia atorium) or 5 (Pyrus) or indefinite (Fragaria and Rosa), apocarpous rarely syncarpous, ovary superior sometimes inferior (Pyrus), axile placentation, nectar secreting disc present between stamens and carpels; when syncarpous the placentation is axile, if apocarpous then basal.
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Fruit:
Variable; drupe (Prunus), etario of achenes (Potentilla) berry (Eriobotrya japonica), pome (Pyrus).
Seed:
Non-endospermic.
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Pollination:
Entomophilous-insects are attracted by nectar, colour, aroma or protandrous nature.
Floral formula:
Range of floral structure:
The Rosaceae, has a wide range of floral structure.
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In the sub-family Spiraeoideae the thalamus is flat or slightly concave but never a deep cup or a convex receptacle. Flowers are pentamerous with 10 – α stamens, 5 carpels which may be free as in Spiraea or fused as in Lindleya.
In the sub-family Pomoideae the thalamus is a deep cup. Flowers pentamerous with 20 or more stamens; carpels 4 or 5 syncarpous and also fused with the inner wall of the cup like thalamus e.g. Pyrus, Crataegus, Cotoneastor etc.
In the Rosoideae the thalamus is cup shaped as in Rosa or convex as in Fragaria and Rubus. Epicalyx is found in Alchemilla and Potentilla. Calyx and corolla five each, stamens α. In Alchemilla unisexual and apetalous flowers may be found. In Agrimonia the stamens α to 1. Carpels α e.g. Rosa, Potentialla Fragaria, Rubus; in Ulmaria only 10 carpels on a flat or concave thalamus.
In sub-family Neuradoideae the thalamus is cup shaped and 5-10 carpels arise from the base of the cup and fused with each other.
In the Prunoideae a deep cup shaped thalamus is found; on the margin of the thalamus 5 sepals and petals each, 10-20 or more stamens arise but only one carpel arises from the base of the cup. The ovary contains only a pair of pendulous ovules.
In the Chrysobalanoideae the thalamus is again a deep cup and there is only one carpel at the base of the cup. But here the style is basal and not terminal and ovule ascending and not pendulous, in several genera the flowers may be zygomorphic. This sub-family has been considered as a connecting link between Prunoideae on the one hand and Papilionaceae on the other.
Distribution of Rosaceae:
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It is commonly known as rose family. The plants of the family are world wide in distribution and are abundant in Europe, N. America and Eastern Asia. It contains 115 genera and 3200 species out of which 257 species are found in India.
Economic Importance of Rosaceae:
1. Fruits:
The fruits of Pyrus malus (H. seb), Pyrus communis (H. Nakh), Prunus persica (II. Aru), Prunus amygdalus (H. Badam), Prunus domestica (H. Alucha), Prunus armeniaca (H. Khuwani), Eriobotrya japonica (H. Loqat) are relished by all. Fragaria vesca is strawberry; black berries and raspberries belong to Rubus; Cydonia oblonga is Quince.
2. Medicinal:
The petals of Rosa are used in making Gulkand, rose water and rose-scent.
The fruits of Prunus domestica are given in leucorrhoea and irregular menstruation. The roots of Rubus fruticosus are used in dysentery and whooping cough. Crateagus ox. is a very good homeopathic medicine for heart disease.
The fruits of Eriobotrya japonica are sedative and used in allaying vomiting and thirst.
3. Wood:
The wood of Cydonia indica, Crataegus oxyacantha is used in making tool handles. The branches of Cydonia indica are excellent walking sticks.
4. Ornamental:
Rosa alba, Rosa moschata, Potentilla, Spiraea are commonly grown in gardens. Rosa damascena (Damascus rose) and R. centifolia are cultivated for otto (itr) or roses. Oil is extracted from Prunus amygdalus (Badam oil).
Affinities of Rosaceae:
Rosaceae is related to Leguminosae and Saxifragaceae due to the presence of stipules, pentamerous flowers, torus, and monocarpellary pistil. The Chrysobalanoideae with zygomorphy connects the Rosaceae with the Papilionaceae. In Acioa the filaments may be fused as in Papilionaceae.
The members of the Rosaceae are very much like that of the Ranunculaceae in number of floral parts, apocarpous condition but differ in shape of the thalamus i.e. thalamus in Rosaceae is cup shaped with carpels either standing or embedded in the bottom of the cup and in Ranunculaceae in the form of a cone.
Primitive characters:
1. Plants mostly shrubs, trees and climbers.
2. Leaves stipulate and simple, alternate in most genera.
3. Flowers hermaphrodite and actinomorphic.
4. Petals free and numerous.
5. Stamens numerous and polyandrous.
6. Gynoecium polycarpellary and apocarpous.
Advanced characters:
1. A few plants herbaceous (Potentilla and Fragaria).
2. Leaves compound (Rosa).
3. Flowers perigynous or epigynous and in a few unisexual.
4. Calyx gamosepalous.
5. Gynoecium monocarpellary.
6. In Pyrus gynoecium bi-to-penta-carpellary and syncarpous.
7. Ovules campylotropus.
8. Seeds non-endospermic.
Common plants of the family:
1. Pyrus malus (H. Seb):
Tree commonly cultivated for fruit.
2. Rosa indica:
Cultivated for showy and fragrant flowers.
3. Fragaria vesca:
Largely cultivated for fruits.
4. Prunus:
Small sized tree cultivated for fruits in temperate climate.
5. Potentilla:
Herbs with yellow or red flowers.
6. Eriobotrya japonica (H. Loqat):
Native of Japan and cultivated for fruits.
Division of the family and chief genera:
Focke in Pflanzenfamilien divided the family Rosaceae into 6 sub-families on the basis of floral construction (shape of torus, position and number of stamens and carpels) and fruit:
1. Spiraeoideae:
Carpels 12-1 usually 5-2, whorled; neither on special carpophore nor shunk in receptacle with 2 or more ovules in each carpel; fruit usually dehiscent; stipules often absent. Spiraea, Quillaja.
2. Pyroideae (Pomoideae):
Carpels 5-2 united to inner wall of receptacle; usually syncarpous; axis fleshy in fruits: stipules present. Pyrus, Sorbus.
3. Rosoideae:
Carpels indefinite rarely one on carpophore sometimes enclosed in axis in fruits, frut one seeded, indehiscent. Rubus, Fragaria, Potentilla.
4. Neuradoideae:
Thalamus cup shaped, carpels 5 to 10 syncarpous. Neurada, Grielum.
5. Prunoideae:
Carpel one rarely 2 to 5 free of torus; fruit drupe; ovules pendulous, flower regular. Prunus, Nuttalia.
6. Chrysobalanoideae:
Thalamus deep and cup shaped; flower zygomorphic; carpel one, ovary superior. Chrysobalanus, Hirtella.
The sub-family viz., Neuradoideae and Chrysobalanoideae are also ranked as families by some taxonomists.
Important Types of Rosaceae:
1. Potentilla:
Habit:
A perennial herb.
Root:
Tap root, branched.
Stem:
Erect, herbaceous, diffusely spreading, branches hairy, solid.
Leaves:
Petiolate, digitately compound with 3 to 5 leaflets, stipulate.
Inflorescence:
Terminal spreading panicle.
Flower:
Bracteate pedicellate, complete, hermaphrodie, pentamerous, actinomorphic, hypogynous, red in colour.
Epicalyx:
Five outer leaves smaller and alternating with sepals.
Calyx:
Sepals 5, persistent, valvate in bud.
Corolla:
Petals 5, polypetalous, rosaceous, red in colour, valvate aestivation, inferior.
Androecium:
Stamens indefinite, anthers dithecous, filament short.
Gynoecium:
Carpels indefinite, very small, apocarpous, crowded on small receptacle, ovary superior, single ovule in each carpel; styles short, lateral and persistent; stigma minute.
Floral formula:
2. Rosa indica (Fig. 55.2 and 55.3):
Habit:
A perennial prickly shrub.
Root:
Tap, branched and perennial.
Stem:
Erect, branched, woody, cylindrical, prickly, solid.
Leaf:
Alternate, petiolate, stipulate, stipules adnate, imparipinnately compound, leaflet ovate, serrate margin.
Leaflet:
Acute apex, unicostate reticulate venation.
Inflorescence:
Solitary flowers.
Flower:
Pedicellate, hermaphrodite, complete, actinomorphic, pentamerous, perigynous, white or red.
Calyx:
Sepals 5, gamosepalous, green, persistent, narrowly lenceolate, odd sepal posterior, quincuncial aestivation.
Corolla:
Petals 5, polypetalous, large, rosaceous, quincuncial aestivation.
Androecium:
Stamens indefinite, polyandrous, anthers yellow, versatile, filament slender, dithecous, introrse.
Gynoecium:
Polycarpellary, apocarpous, ovaries enclosed in calyx tube, basal placentation, styles free, stigma terminal.
Floral formula:
