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  Section: Kingdom Plantae » Famalies
 
 
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Family Amaranthaceae

 
     
 

Amaranthaceae Juss.

Including Deeringiaceae J.G. Agardh, Subscariosaceae Dulac

Habit and leaf form. Shrubs (usually), or herbs. ‘Normal’ plants. Plants succulent (occasionally, if the halophytic Hemichroa is referred here rather than to Chenopodiaceae), or non-succulent (mostly). With a basal aggregation of leaves (occasionally, e.g. in Ptilotus), or with neither basal nor terminal aggregations of leaves (usually). Self supporting, or climbing (occasionally). Leaves alternate, or opposite; ‘herbaceous’ (mostly), or fleshy (perhaps only Hemichroa); sheathing, or non-sheathing; simple. Lamina entire; one-veined, or pinnately veined. Leaves exstipulate. Lamina margins entire. Domatia commonly occurring in the family.

General anatomy. Plants commonly with ‘crystal sand’.

Leaf anatomy. Abaxial epidermis not papillose.


Adaxial hypodermis absent. Main veins embedded. Minor leaf veins without phloem transfer cells (Amaranthus, Celosia).

Stem anatomy. Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissue centrifugal. Cortical bundles absent. Medullary bundles present (commonly), or absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring, or anomalous; when anomalous, via concentric cambia. ‘Included’ phloem present, or absent. Xylem with libriform fibres; with vessels. Vessel end-walls simple. Primary medullary rays wide. Wood storied (Charpenteria, Iresine), or partially storied (?), or not storied (?); parenchyma paratracheal. Sieve-tube plastids P-type; type III (a).

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or andromonoecious, or gynomonoecious, or dioecious, or androdioecious, or polygamomonoecious (rarely).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (usually with conspicuous, persistent bracts and bracteoles); in cymes, or in spikes, or in heads. The ultimate inflorescence unit when flowers aggregated, cymose. Inflorescences racemes of cymes; with involucral bracts (rarely), or without involucral bracts; pseudanthial, or not pseudanthial. Flowers bracteate; bracteolate; regular; cyclic; tricyclic. Free hypanthium absent (except, dubiously, in some Ptilotus species, where the androecial tube is adnate to the calyx). Hypogynous disk absent.

Perianth sepaline (dry and scarious); 3–5; sepaloid, or petaloid. Calyx 3–5; polysepalous, or gamosepalous (partially); regular; non-fleshy; persistent (dry, stiff and scarious); accrescent (e.g. some Ptilotus species), or non-accrescent; imbricate; when K 5, with the median member posterior.

Androecium (1–)2, or 5, or 6–10. Androecial members free of the perianth, or adnate (to the perianth or disk); markedly unequal (usually, by contrast with most Chenopodiaceae), or all equal (more or less, e.g. in some Ptilotus species); usually basally coherent (by contrast with most Chenopodiaceae); 1 adelphous (the filaments usually connate for all or part of their length into a membranous tube); 1 whorled. Androecium exclusively of fertile stamens, or including staminodes (commonly, by contrast with most Chenopodiaceae — some androecial members may lack anthers, also there are often ‘petaloid enations’ or ‘pseudostaminodial scales’ alternating with the true androecial members). Staminodes when present, 1–3, or 2, or 3, or 5; in the same series as the fertile stamens; when present, petaloid, or non-petaloid. Stamens (1–)3–5; reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositisepalous. Anthers dehiscing via longitudinal slits; introrse; unilocular to bilocular; bisporangiate, or tetrasporangiate. Endothecium developing fibrous thickenings, or not developing fibrous thickenings (very rarely). Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer; of the ‘monocot’ type. Tapetum glandular. Pollen monosiphonous; shed as single grains. Pollen grains aperturate; 6–20 aperturate; foraminate; spinulose; 3-celled.

Gynoecium 2–3 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary 1 locular; sessile to stipitate. Gynoecium non-stylate, or stylate. Styles 1–3. Stigmas 1–3; dry type; papillate; Group II type. Placentation basal. Ovules in the single cavity 1, or 2–5; ascending, or pendulous (but from a basal funicle, subtribe Achyranthinae, Ptilotus etc.); non-arillate; campylotropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle (rarely), or not contributing to the micropyle. Endothelium not differentiated. Polar nuclei fusing prior to fertilization. Antipodal cells formed; initially 3; proliferating (Pupalia), or not proliferating (usually). Synergids hooked (sometimes with filiform apparatus). Endosperm formation nuclear. Embryogeny solanad, or chenopodiad.

Fruit fleshy, or non-fleshy; not an aggregate; dehiscent, or indehiscent; a capsule, or capsular-indehiscent, or a berry, or a drupe, or a nut (often a utricle or nutlet); without fleshy investment. Capsules circumscissile (commonly), or splitting irregularly. Seeds non-endospermic (strictly speaking). Perisperm present (abundant, mealy). Seeds with starch. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (1/1); curved. The radicle dorsal. Testa smooth (usually shiny).

Physiology, biochemistry. Cyanogenic, or not cyanogenic. Alkaloids present, or absent. Iridoids not detected. Proanthocyanidins absent. Flavonols present, or absent; when present, quercetin. Ellagic acid absent (4 species, 4 genera). Betalains present. Saponins/sapogenins present, or absent. Plants often accumulating free oxalates. Inulin not found. C3 and C4, or C3-C4 intermediate. C3 physiology recorded directly in Aerva, Achyranthes, Alternanthera, Arthraerua, Celosia, Digera, Pupalia. C4 physiology recorded directly in Achanthochiton, Aerva, Alternanthera, Amaranthus, Brayulinea, Froelichia, Gomphrena, Gossypianthes, Guillemenia, Lithophila, Tidestromia. C3-C4 intermediacy in Alternanthera ficoides and A. tenella. Anatomy C4 type (Acnidia, Achyranthes, Achanthochiton, Aerva, Alternanthera, Amaranthus, Brayulinea, Celosia, Froelichia, Gomphrena, Pfaffia, Tidestromia, etc.), or non-C4 type (Achyranthes, Alternanthera, Celosia, Centemopsis, Dasysphaera, Digera, Pupalia, Sericicomopsis etc.).

Geography, cytology. Temperate, sub-tropical, and tropical. Widespread. X = 6–13, 17(+).

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG (1998) Eudicot; core Eudicot; neither Rosid nor Asterid. APG 3 (2009) Order: Caryophyllales.

Species 850. Genera 74; Achyranthes, Achyropsis, Acnida, Aerva, Allmania, Alternanthera, Amaranthus, Arthraerua, Blutaparon, Bosea, Brayulinea, Calicorema, Celosia, Centema, Centemopsis, Centrostachys, Chamissoa, Charpentiera, Chionothrix, Cyathula, Dasysphaera, Dasysphaera, Deeringia, Digera, Eriostylos, Froelichia, Gomphrena, Gossypianthus, Guilleminea, Hebanthe, Hemichroa (~ Chenopodiaceae), Henonia, Herbstia, Hermbstaedtia, Indobanalia, Irenella, Iresine, Kyphocarpa, Lagrezia, Leucosphaera, Lithophila, Lopriorea, Marcelliopsis, Mechowia, Nelsia, Neocentema, Nothosaerva, Nototrichium, Nyssanthes, Pandiaka, Pfaffia, Philoxerus, Pleuropetalum, Pleuropterantha, Polyrhabda, Pseudogomphrena, Pseudoplantago, Pseudosericocoma, Psilotrichopsis, Psilotrichum, Ptilotus, Pupalia, Quaternella, Rosifax, Saltia, Sericocoma, Sericocomopsis, Sericorema, Sericostachys, Siamosia, Stilbanthus, Tidestromia, Trichuriella, Volkensinia, Woehleria, Xerosiphon.

Economic uses, etc. A few cultivated ornamentals, e.g. Amaranthus, Gomphrena, Iresine, and some noxious weeds, notably from Amaranthus, Iresine, Acnida.

Illustrations.
• Technical details: Amaranthus, Gomphrena.
• Technical details: Achyranthes (Thonner).
• Amaranthus blitum: Eng. Bot. 177, 1867.
• Celosia cristata var. coccinea: as C. coccinea, Bot. Reg 1834 (1836).
• Ptilotus polystachyus: Bot. Reg. 1839, 28.

Quotations
But propt on beds of amaranth and moly,
How sweet . . . .
To watch the long bright river drawing slowly
His waters from the purple hill -
(Tennyson, ‘Song of the Lotos-eaters’)

 
     
 
 
     



     
 
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