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In this article we will discuss about:- 1. Characters of Amaranthaceae 2. Distribution of Amaranthaceae 3. Economic Importance 4. Affinities 5. Important Types.
Characters of Amaranthaceae:
Plants mostly herbs, a few shrubs, leaves exstipulate and simple; opposite or alternate, hairy; flowers small, incospicuous and usually with bracts and bracteoles, actinomorphic, arranged in spikes or racemes; perianth 2 to 5, uniseriate, green or coloured, free or united; stamens 3 to 5 free, dithecous, antiphyllous (opposite the perianth segments); gynoecium bi or tri-carpellary, unilocular with a single basal ovule; fruit one seeded nutlet.
A. Vegetative characters:
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Habit:
Mostly herbs, rarely shrubs or undershrubs (Deeringia), annual or perennial (Bosia, Ptilotus).
Root:
A branched tap root.
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Stem:
Aerial, herbaceous or woody, erect or straggling, cylindrical, or angular, branched, solid, hairy, green or striped green.
Leaves:
Simple, alternate or opposite, petiolate, exstipulate, reddish in colour, unicostate reticulate venation.
B. Floral characters:
Inflorescence:
Axillary or terminal spikes (Achyranthes, Digera). Some times in cymose panicles.
Flower:
Bracteate, sessile or sub-sessile, bracteolate, bracteoles two, actinomorphic, hermaphrodite or unisexual hypogynous, small inconspicuous, green or variously coloured.
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Perianth:
Usually five tepals, free or united, sometimes two or three (Amaranthus), dry membranous, valvate or twisted, sometime, hairy, green or coloured, persistent, inferior.
Androecium:
Stamens 5 or 3 (Amaranthus), free or united, staminodes sometimes present, introrse, dithecous or monothecous (Alternanthera). In Achyranthes 5 fimbriated scales alternate with 5 fertile stamens.
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Gynoecium:
Bicarpellary, or tricarpellary; syncarpous, ovary superior, unilocular, usually one campylotropous ovule; basal placentation; style short or filiform; stigma 2 or 3.
Fruit:
Dry one seeded achene or several seeded capsule or one to several seeded berry.
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Seed:
Endospermic with polished testa, kidney-shaped embryo curved.
Pollination:
Mostly anemophilous and in some plants entomophilous.
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Floral formula:
Distribution of Amaranthaceae:
The family Amaranthaceae is commonly called ‘Amaranth family’. It is a small family comprising 65 genera and 850 species which are chiefly represented in tropical and temperate regions. In India it is represented by 50 species.
Economic Importance of Amaranthaceae:
The Amaranthaceae is of little economic importance.
Food:
Seeds of Amaranthus caudatus are edible. Amaranthus cruentus and A. frumentacea are raised as cereals by primitive tribes in Tropical Asia. The leaves of Amaranthus viridis, A. spinosus and A. tricolor are also used as vegetables.
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Medicinal:
Achyranthes aspera is diuretic and purgative. Decoction of Aerua tomentosa is used to remove swellings. The stem and leaves of Alternanthera are used in snake-bite. The flowers and seeds of Digera muricata (syn. D. arvensis) are given for urinary discharges.
Dye:
Leaves of Bosia amherstiana yield a black dye. The fruit juice of Deeringia is a substitute for red ink.
Weeds:
Some genera are weeds e.g. Amaranthus, Celosia, Digera, Achyranthes, Gomphrena etc.
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Ornamentals:
Celosia cristata (Cockscomb), Gomphrena globosa (Globe amaranthus) are cultivated in gardens.
Primitive characters:
1. Plants under-shrubs or shrubs (Bosia, Ptilotus).
2. Leaves simple and alternate.
3. Flowers actinomorphic, hypogynous and hermaphrodite.
4. Anthers dithecous.
5. Seeds endospermic.
Advanced characters:
1. Plants mostly herbs.
2. Leaves exstipulate, opposite (Gomphrena, Alternanthera).
3. Flowers small, inconspicuous and unisexual (Aerua, Amaranthus).
4. Perianth gamophyllous.
5. Number of stamens reduced to 2 or 3.
6. Gynoecium bicarpellary and syncarpous.
7. Basal placentation.
8. One ovule in a carpel.
9. Ovule campylotropous.
10. Anemophilous pollination.
Affinities of Amaranthaceae:
Engler and Prantl regarded the Amaranthaceae as primitive but Hutchinson, Takhtajan and Cronquist regard it as one of the advanced families of dicots. Many taxonomists have felt that the family is not primitive and has been derived from caryophyllous ancestors.
The Amaranthaceae is related to the Chenopodiaceae by the possession of monochlamydous flowers, uniseriate stamens and single basal ovule. However the Amaranthaceae differs from the Chenopodiaceae in having scarious bracts, membranous perianth and congested inflorescence.
Common plant of the family:
1. Aerua javanica:
A hoary tomentose under-shrub.
2. Achyranthes aspera:
Chaff flowered, common weed of waste places.
3. Alternanthera sessilis:
A prostrate herb of damp places.
4. Bosia amherstiana:
A glabrous shrub with edible berries.
5. Celosia (Cockscomb):
A cultivated herb in different colours.
6. Digera muricata:
A wild herb of winter.
7. Gomphrena globosa:
Button flower of Globe amaranth, cultivated for deep pink heads.
8. Cyathula tomentosa:
Densely woody herb.
Division of the family and chief genera:
Schinz divided the family into two sub-families and tribes as follows:
Sub-family I. Amaranthoideae:
Stamens four loculed or anthers dithecous, ovary 1 to 2 ovuled.
Tribe 1. Celosieae:
Ovules 2 to many per carpel, e.g. Celosia.
Tribe 2. Amarantheae:
Ovary with one ovule, e.g. Amaranthus, Achyranthes.
Sub-family II. Gomphrenoideae:
Stamens two loculed or anthers monothecous; ovary one ovuled.
Tribe 3. Brayulineae:
Flowers in axillary fascicles or solitary, e.g. Brayulinea.
Tribe 4. Gomphreneae:
Inflorescence spikelet or capitate e.g. Gomphrena, Alternanthera.
Important Types of Amaranthaceae:
1. Amaranthus viridis (H. Chaulai):
Habit:
Wild or cultivated annual, herb.
Root:
Branched tap root.
Stem:
Aerial, erect, herbaceous, angular, branched, green or striped, hairy.
Leaves:
Alternate, simple, petiolate, exstipulate, ovate, entire or repand, acute, hairy or glabrous, unicostate reticulate.
Inflorescence:
Axillary or terminal spikes.
Flower:
Bracteate, sessile, incomplete, unisexual, actinomorphic, hypogynous, small, green.
Male flower:
Perianth:
Tepals 3, distinct, ovate, acute keeled, green, valvate, inferior.
Androecium:
Stamens 3, free, antiphyllous, anthers dithecous, basifixed, introrse.
Gynoecium may be rudimentary.
Female flower:
Perianth:
Tepals 2, ovate, green, inferior, valvate.
Androecium:
Absent.
Gynoecium:
Bicarpellary, syncarpous, ovary superior, unilocular, basal placentation, ovule one; style three, persistent, stigma capitate, hairy.
Fruit:
An indehiscent utricle.
2. Achyranthes aspera (Fig. 90.1):
Habit:
Wild perennial herb of waste places, 30 to 90 cm high.
Root:
Much branched tap root.
Stem:
Herbaceous above and woody below, aerial, erect, quadrangular, rough, branched, solid, hairy, green.
Leaves:
Opposite, simple, petiolate, exstipulate, obovate, repand, acuminate, both the surfaces hairy, unicostate reticulate.
Inflorescence:
Spike; flowers arranged along a pubescent axis that becomes rigid and much elongated during fruiting-as much as 60 cm.
Flower:
Bracteate, bracts persistent acuminate, ending in a spine, bracteolate, sessile, complete, hermaphrodite, actinomorphic, hypogynous, small, green.
Perianth:
Tepals 5, polyphyllous, ovate, persistent, green, glabrous, twisted, inferior.
Androecium:
5 fertile stamens alternating with 5 sterile and fimbriated scale-like staminodes; fertile stamens antiphyllous, anthers dithecous, basifixed, introrse.
Gynoecium:
Bicarpellary, syncarpous, ovary superior, unilocular, one ovuled, basal placentation, style filiform, stigma capitate.
Fruit:
An indehiscent achene enclosed within persistent perianth.
Seed:
Endospermic.
Floral formula:
