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Kingdom-Plantae
Class -Magnoliopsida
Order-Caryophyllales
Family-Amaranthaceae
Genus-Amaranthus L.
Description
Amaranthus is a cosmopolitan genus of annual or short-lived perennial plants collectively known as amaranths. Some amaranth species are cultivated as leaf vegetables, pseudocereals, and ornamental plants. Catkin-like cymes of densely packed flowers grow in summer or autumn. Amaranth varies in flower, leaf, and stem color with a range of striking pigments from the spectrum of maroon to crimson and can grow longitudinally from 1 to 2.5 metres tall with a cylindrical, succulent, fibrous stem that is hollow with grooves and bracteoles when mature.There are approximately 75 species in the genus, 10 of which are dioecious and native to North America with the remaining 65 monoecious species endemic to every continent (except Antarctica) from tropical lowlands to the Himalayas.Numerous traits and applications are shared by species of this genus and those of the closely related genus Celosia. The genus is harvested for amaranth grain. Some species' leaves are also consumed.Throughout the genus, amaranth is a herbaceous plant or shrub that can be either annual or perennial. Flowers differ between species depending on whether they have three or five tepals and stamens, but all members of the family have a 7-porate pollen particle shape. The genus' species share a C4 photosynthetic pathway and have concentric rings of vascular bundles that effectively fix carbon. Depending on the species, leaves range in size from 6.5 to 15 centimetres and have an oval or elliptical shape. Most leaves are whole, simple, and have entire margins.A primary root and deeper spreading secondary fibrous root structures are present in amaranth. Large panicles that range in size from terminal to axial, as well as in colour and sex, are the inflorescences. The fluorescence tassel can be straight or curved, and its width and length vary depending on the species. Flowers have a very tiny, bristly perianth with pointed bracts, and they can be either bisexual or unisexual. Either monecious or dioecious species can be found in this genus. Fruits are produced as unilocular pixdios, which open when they reach maturity. The urn holding the seed is released from the unilocular pixdio's top (operculum). Round seeds with a diameter of 1 to 1.5 millimetres have a variety of colours and a smooth, lustrous seed coat.
Amaranth grain contains phytochemicals such polyphenols, saponins, tannins, and oxalates that are not considered nutrients but may behave as antinutrients. Cooking reduces the content and antinutrient impact of these substances.
Taxonomy
Amaranthus has extensive physical variability between and even within certain species. The Amaranthaceae, which is a subfamily of the Carophyllales, includes Amaranthus. The 75 species spread across six continents of this genus are not easily distinguished from one another. Amaranthus has historically been regarded by systematists as a "difficult" genus that hybridises frequently, which complicates taxonomy.In 1955, Sauer divided the genus into two subgenera, Acnida (L.) Aellen ex K.R. Robertson and Amaranthus, distinguishing only between monoecious and dioecious species. Despite the widespread acceptance of this categorization, additional infrageneric classification has been is also still to distinguish this incredibly complex group. Later, Acnida, Amaranthus, and Albersia were split into three subgenera by Mosyakin and Robertson (1996). Albersia was added as a subdivision because of its circumcise, indehiscent fruits and three elliptic to linear tepals, which are unique to the species in this subgenus. A mix of floral traits, reproductive methods, geographic distribution, and molecular data are used to support the classification of these groups.Maximum parsimony and Bayesian analyses of the nuclear and chloroplast DNA used in the phylogenies of Amaranthus show five clades within the genus.Although the number of species in Amaranthus is disputed due to hybridization and species ideas, the genus is known to contain three recognised subgenera and 75 species. According to Sauer's (1955) suggested classification, infrageneric categorization emphasises inflorescence, flower characteristics, and whether a species is monoecious or dioecious. Amaranth is classified taxonomically based on the form of the bracteoles that are present on the stem. Wild species' bracteoles are longer than those of domesticated species. Three subgenera—Acnida, Amaranthus, and Albersia—are included in a modified infrageneric classification of Amaranthus, with sections within each subgenus serving as additional taxonomic distinctions.
The later series of domestication to come is still unknown, but it is almost certain that A. hypochondriacus is the common ancestor of the cultivated grain species. There have been competing theories on the number of domestication events that took place for the three grain species. Clear groupings that suggest independent domestication events in South America and Central America are supported by phylogenetic and geographic evidence. While A. caudatus, A. hypochondriacus, and A. quentiensis are indigenous to Central and North America, A. hybridus may have originated in South America.
Ecology
Amaranth weed species have been an issue for farmers since the mid-1990s because of their lengthy germination times, quick development, and high rates of seed production. This is partly because tillage has decreased, fewer herbicides are being used, and some species where herbicides have been used more frequently have developed herbicidal resistance. In the United States and Canada, the following nine species of Amaranthus are regarded as noxious weeds.A. palmeri has developed a new strain that is glyphosate-resistant and thus cannot be killed by herbicides that contain the substance. Furthermore, this plant can endure adverse environments. The species Amaranthus palmeri (Palmer amaranth) reduces soybean yields the most and has the ability to do so by 17–68% in field studies. Palmer amaranth is one of the "top five most troublesome weeds" in the Southeast of the United States, and it has already developed resistance to acetolactate synthase inhibitors and dinitroaniline herbicides. Because of this, it is crucial for farmers to correctly identify Amaranthus species when they are still seedlings. Before the species successfully colonises in the crop field and results in appreciable yield decreases, effective weed management must be implemented.
Uses
Squalene, which makes up around 5% of the total fatty acids in amaranth, is extracted and used as a cheaper vegetable-based substitute for shark oil in dietary supplements and cosmetics. The Hopi (a tribe in the western United States) used the blossoms of the "Hopi Red Dye" amaranth as a source for a rich red dye. A synthetic dye that resembles the natural amaranth colours known as betalains was also given the name "amaranth" for this reason. In North America and the European Union, this synthetic dye is also referred to as Red No. 2 and E123, respectively. Several well-known ornamental plants are also found in the genus, including Amaranthus caudatus (love-lies-bleeding), a robust, hardy annual with dark purplish blooms crammed in attractive drooping spikes.
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