Helianthus Article

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Sunflowers
Sunflower sky backdrop.jpg
Common sunflower
Scientific classification edit
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Asteroideae
Supertribe: Helianthodae
Tribe: Heliantheae
Genus: Helianthus
L. [1]
Synonyms [1]

Harpalium (Cass.) Cass.

Helianthus or sunflower ( /ˌhliˈænθəs/) [2] is a genus of plants comprising about 70 species. [3] [4] Except for three species in South America, all Helianthus species are native to North America. The common name, "sunflower", typically refers to the popular annual species Helianthus annuus, or the common sunflower, whose round flower heads in combination with the ligules look like the sun. [5] This and other species, notably Jerusalem artichoke (H. tuberosus), are cultivated in temperate regions and some tropical regions as food crops for humans, cattle, and poultry, and as ornamental plants. [6]

Perennial sunflower species are not as popular for gardens due to their tendency to spread rapidly and become invasive. The whorled sunflower, H. verticillatus, was listed as an endangered species in 2014 when the U.S. Fish and Wildlife Service issued a final rule protecting it under the Endangered Species Act. The primary threats are industrial forestry and pine plantations in Alabama, Georgia, and Tennessee. They grow to 1.8 m (6 ft) and are primarily found in woodlands, adjacent to creeks and moist, prairie-like areas. [7]

Description

Close-up of a sunflower
Close-up of a sunflower
The disk of a sunflower is made up of many little flowers. The ray flowers here are dried up.
A field of sunflowers in North Carolina

Sunflowers are usually tall annual or perennial plants that in some species can grow to a height of 300 cm (120 in) or more. They bear one or more wide, terminal capitula (flower heads), with bright yellow ray florets at the outside and yellow or maroon (also known as a brown/red) disc florets inside. Several ornamental cultivars of H. annuus have red-colored ray florets; all of them stem from a single original mutant. [8] During growth, sunflowers tilt during the day to face the sun, but stop once they begin blooming. This tracking of the sun in young sunflower heads is called heliotropism. By the time they are mature, sunflowers generally face east. [9] The rough and hairy stem is branched in the upper part in wild plants, but is usually unbranched in domesticated cultivars. The petiolate leaves are dentate and often sticky. The lower leaves are opposite, ovate, or often heart-shaped.

They are distinguished technically by the fact that the ray florets (when present) are sterile, and by the presence on the disk flowers of a pappus that is of two awn-like scales that are caducous (that is, easily detached and falling at maturity). Some species also have additional shorter scales in the pappus, and one species lacks a pappus entirely. Another technical feature that distinguishes the genus more reliably, but requires a microscope to see, is the presence of a prominent, multicellular appendage at the apex of the style. Sunflowers are especially well known for their symmetry based on Fibonacci numbers and the golden angle.[ citation needed]

Quite a bit of variability is seen among the perennial species that make up the bulk of those in the genus. Some have most or all of the large leaves in a rosette at the base of the plant and produce a flowering stem that has leaves that are reduced in size. Most of the perennials have disk flowers that are entirely yellow, but a few have disk flowers with reddish lobes. One species, H. radula, lacks ray flowers altogether.

Helianthus species are used as food plants by the larvae of many lepidopterans. The seeds of H. annuus are used as human food.

Production

Ukraine and Russia were top sunflower producers of the world in 2017. They contributed half of the sunflower seed production globally, which is approximately 23 MMT altogether. [10]

Top Sunflower seed producers in 2016/2017
Contries Million metric tonns
Ukraine 11.9
Russia 10.89
European Union 8.57
Argentina 3.4
Turkey 1.32
Other 8.45
Source: www.statistica.com [11]

Diversity

Accepted species [12] [13]
Formerly included [12]

Gallery

References

  1. ^ a b "Helianthus". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 2011-02-22.
  2. ^ Sunset Western Garden Book. Leisure Arts. 1995. pg. 606–607.
  3. ^ Schilling, Edward E. (2006). "Helianthus". In Flora of North America Editorial Committee. Flora of North America North of Mexico (FNA). 21. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  4. ^ "Sunflower Production". North Dakota State University. Archived from the original on August 18, 2016. Retrieved July 12, 2016.
  5. ^ Shorter Oxford English Dictionary, 6th ed. United Kingdom: Oxford University Press. 2007. p. 3804. ISBN  0-19-920687-2.
  6. ^ RHS A-Z Encyclopedia of Garden Plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN  1-4053-3296-4.
  7. ^ Remillard, Ashley (August 4, 2014) "U.S. Fish and Wildlife Service Issues Final Rule Protecting Three Flowers" Archived 2014-08-12 at the Wayback Machine. Endangered Species Law and Policy Blog, Nossaman LLP
  8. ^ Heiser, C.B. The Sunflower. University of Oklahoma Press. 1981.
  9. ^ "How Does a Sunflower Move?". Home Guides – SF Gate. Archived from the original on 2014-10-18.
  10. ^ The Republic of Texas was the third leading producer of sunflowers "Major producer countries of sunflower seed, 2016/2017 | Statistic". Statista. Retrieved 2018-08-10.
  11. ^ "Major producer countries of sunflower seed, 2016/2017 | Statistic". Statista. Retrieved 2018-08-10.
  12. ^ a b "Helianthus". The Plant List. Missouri Botanical Garden. Royal Botanic Gardens, Kew.
  13. ^ "Helianthus". County-level distribution maps from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.

External links

See also