Sunflower: Wikis

  
  
  

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Sunflower
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Helianthoideae
Tribe: Heliantheae
Genus: Helianthus
Binomial name
Helianthus annuus
L.
Whole seed (right) and kernel with hull removed (left)

Sunflowers (Helianthus annuus) are annual plants native to the Americas, that possess a large inflorescence (flowering head).

Contents

Description

Head displaying florets in spirals of 34 and 55 around the outside

What is usually called the flower is actually a head (formally composite flower) of numerous florets (small flowers) crowded together. The outer florets are the sterile ray florets and can be yellow, maroon, orange, or other colors. The florets inside the circular head are called disc florets, which mature into seeds

The florets within the sunflower's cluster are arranged in a spiral pattern. Typically each floret is oriented toward the next by approximately the golden angle, 137.5°, producing a pattern of interconnecting spirals where the number of left spirals and the number of right spirals are successive Fibonacci numbers. Typically, there are 34 spirals in one direction and 55 in the other; on a very large sunflower there could be 89 in one direction and 144 in the other.[1][2][3] This pattern produces the most efficient packing of seeds within the flower head.[4][5][6]

Heliotropism

Sunflowers in the bud stage exhibit heliotropism. At sunrise, the faces of most sunflowers are turned towards the east. Over the course of the day, they follow the sun from east to west, while at night they return to an eastward orientation. This motion is performed by motor cells in the pulvinus, a flexible segment of the stem just below the bud. As the bud stage ends, the stem stiffens and the blooming stage is reached.

Sunflowers in their blooming stage lose their heliotropic capacity. The stem becomes "frozen", typically in an eastward orientation.[citation needed] The stem and leaves lose their green color.

The wild sunflower typically does not turn toward the sun; its flowering heads may face many directions when mature. However, the leaves typically exhibit some heliotropism.

History

Sunflower field

The sunflower is native to the Central Americas. The evidence thus far is that it was first domesticated in Mexico, by at least 2600 BC.[7] It may have been domesticated a second time in the middle Mississippi Valley, or been introduced there from Mexico at an early date, as maize was. The earliest known examples of a fully domesticated sunflower north of Mexico have been found in Tennessee and date to around 2300 BC. Many indigenous American peoples used the sunflower as the symbol of their solar deity, including the Aztecs and the Otomi of Mexico and the Incas in South America. Francisco Pizarro was the first European to encounter the sunflower in Tahuantinsuyo, Peru. Gold images of the flower, as well as seeds, were taken back to Spain early in the 16th century. Some researchers argue that the Spaniards tried to suppress cultivation of the sunflower because of its association with solar religion and warfare.[8]

During the 18th century, the use of sunflower oil became very popular in Europe, particularly with members of the Russian Orthodox Church because sunflower oil was one of the few oils that was not prohibited during Lent.

Cultivation and uses

Worldwide sunflower output

To grow well, sunflowers need full sun. They grow best in fertile, moist, well-drained soil with a lot of mulch. In commercial planting, seeds are planted 45 cm (1.5 ft) apart and 2.5 cm (1 in) deep. Sunflower "whole seed" (fruit) are sold as a snack food, after roasting in ovens, with or without salt added. Sunflowers can be processed into a peanut butter alternative, Sunbutter. In Germany, it is mixed together with rye flour to make Sonnenblumenkernbrot (literally: sunflower whole seed bread), which is quite popular in German-speaking Europe. It is also sold as food for birds and can be used directly in cooking and salads.

Sunflower oil, extracted from the seeds, is used for cooking, as a carrier oil and to produce margarine and biodiesel, as it is cheaper than olive oil. A range of sunflower varieties exist with differing fatty acid compositions; some 'high oleic' types contain a higher level of healthy monounsaturated fats in their oil than even olive oil.

Detail of disk florets.

The cake remaining after the seeds have been processed for oil is used as a livestock feed. Some recently developed cultivars have drooping heads. These cultivars are less attractive to gardeners growing the flowers as ornamental plants, but appeal to farmers, because they reduce bird damage and losses from some plant diseases. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.

Traditionally, several Native American groups planted sunflowers on the north edges of their gardens as a "fourth sister" to the better known three sisters combination of corn, beans, and squash.[9] Annual species are often planted for their allelopathic properties.[citation needed]

However, for commercial farmers growing commodity crops, the sunflower, like any other unwanted plant, is often considered a weed. Especially in the midwestern USA, wild (perennial) species are often found in corn and soybean fields and can have a negative impact on yields.

Sunflowers may also be used to extract toxic ingredients from soil, such as lead, arsenic and uranium. They were used to remove uranium, cesium-137, and strontium-90 from soil after the Chernobyl disaster (see phytoremediation).

Mathematical model of floret arrangement

Illustration of Vogel's model for n=1..500 .

A model for the pattern of florets in the head of a sunflower was proposed by H. Vogel in 1979.[10] This is expressed in polar coordinates

r = c \sqrt{n},
\theta = n \times 137.5^{\circ},

where θ is the angle, r is the radius or distance from the center, and n is the index number of the floret and c is a constant scaling factor. It is a form of Fermat's spiral. The angle 137.5° is related to the golden ratio and gives a close packing of florets. This model has been used to produce computer graphics representations of sunflowers.[11]

Size

Sunflowers most commonly grow to heights between 1.5 and 3.5 m (8–12 ft). Scientific literature reports from 1567, that a 12-m (40 ft), traditional, single-head, sunflower plant was grown in Padua. The same seed lot grew almost 8 m (26 ft) at other times and places (e.g. Madrid). Much more recent feats (past score years) of over 8 m have been achieved in both Netherlands and Ontario, Canada.

Cultural symbol

Varieties

The following are varieties of sunflowers (in alphabetical order):

  • American Giant Hybrid
  • Arnika
  • Autumn Beauty
  • Aztec Sun
  • Black Oil
  • Dwarf Sunspot
  • Evening Sun
  • Giant Primrose
  • Indian Blanket Hybrid
  • Irish Eyes
  • Italian White
  • Kong Hybrid
  • Large Grey Stripe
  • Lemon Queen
  • Mammoth Sunflower
  • Mongolian Giant
  • Orange Sun
  • Peach Passion
  • Peredovik
  • Red Sun
  • Ring of Fire
  • Rostov
  • Skyscraper
  • Soraya
  • Strawberry Blonde
  • Sunny Hybrid
  • Taiyo
  • Tarahumara
  • Teddy Bear
  • Titan
  • Valentine
  • Velvet Queen
  • Yellow Empress

Other species

  • The Maximillian sunflower (Helianthus maximillianii) is one of 38 species of perennial sunflower native to North America. The Land Institute and other breeding programs are currently exploring the potential for these as a perennial seed crop
  • The Sunchoke [1] (Jerusalem artichoke or Helianthus tuberosus) is related to the sunflower, another example of perennial sunflower.
  • The Mexican sunflower is Tithonia rotundifolia. It is only very distantly related to North American sunflowers.
  • False sunflower refers to plants of the genus Heliopsis.

Gallery


See also

Notes

References

  • Pope, Kevin; Pohl, Mary E. D.; Jones, John G.; Lentz, 3 David L.; von Nagy, Christopher; Vega, Francisco J.; Quitmyer Irvy R.; "Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica," Science, 18 May 2001:Vol. 292. no. 5520, pp. 1370–1373.
  • Shosteck, Robt. 1974. Flowers and Plants. An International Lexicon with Biographical Notes. Quadrangle/The New York Times Book Co. 329 pp.
  • Wood, Marcia. June 2002. "Sunflower Rubber?" Agricultural Research. USDA. [2]

External links


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

SUNFLOWER. The common sunflower, known botanically as Helianthus annuus, a member of the natural order Compositae, is a native of the western United States. It is an annual herb with a rough hairy stem 3 to 12 ft. high, broad coarsely toothed rough leaves 3 to 12 in. long, and heads of flowers 3 to 6 in. wide in wild specimens and often a foot or more in cultivated. Double forms are in cultivation, one (globosus fistulosus) having very large globular heads. The plant is valuable from an economic as well as from an ornamental point of view. The leaves are used as fodder, the flowers yield a yellow dye, and the seeds contain oil and are used for food. It is cultivated in Russia and other parts of Europe, in Egypt and India and in several parts of England hundreds of plants are grown on sewage farms for the seeds. The yellow sweet oil obtained by compression from the seeds is considered equal to olive or almond oil for table use. Sunflower oilcake is used for stock and poultry feeding, and largely exported by Russia to Denmark, Sweden and elsewhere. The genus Helianthus contains about fifty species, chiefly natives of North America, a few being found in Peru and Chile. They are tall, hardy annual or perennial herbs, several of which are well known in gardens where they are of easy cultivation in moderately good soil. H. decapetalus is a perennial about 5 ft. high with solitary heads about 2 in. across in slender twiggy branchlets; H. multiflorus is a beautiful species with several handsome double varieties; H. orygalis is a graceful perennial 6 to 10 ft. high, with drooping willow-like leaves and numerous comparatively small yellow flower-heads. H. atrorubens, better known as Harpalium rigidum, is a smaller plant, 2 to 3 ft. high, the flower heads of which have a dark red or purple disk and yellow rays. There are many fine forms of this now, some of which grow 6 to 9 ft. high and have much larger and finer flowers than the type. Other fine species are H. giganteus, 10 to 12 ft.; H. laetiflorus, 6 to 8 ft., and H. mollis, 3 to 5 ft. H. tuberosus is the Jerusalem artichoke.

Since the word "sunflower," or something corresponding to it, existed in English literature before the introduction of Helianthus annuus, or, at any rate, before its general diffusion in English gardens, it is obvious that some other flower must have been intended. The marigold (Calendula officinalis) is considered by Dr Prior to have been the plant intended by Ovid (Met. iv. 269-270) ". Ilia suum, quamvis radice tenetur, Vertitur ad solem; mutataque servat amorem" and likewise the solsaece of the Anglo-Saxon, a word equivalent to solsequium (sun-following). But this movement with the sun is more imaginary than real, the better explanation for the application of the name to a flower being afforded by the resemblance to "the radiant beams of the sun," as Gerard expresses it. The rock-rose (Helianthemuni vulgare) was also termed sunflower in some of the herbals from its flowers opening only in the sunshine. Actinella grandiflora, a pretty perennial 6 to 9 in. high, from the Colorado mountains, is known as the Pigmy sunflower.


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Simple English

Sunflower
File:A
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Asterales
Family: Asteraceae
Tribe: Heliantheae
Genus: Helianthus
Species: H. annuus
Binomial name
Helianthus annuus
L.

The sunflower (Helianthus annuus) is an annual plant in the family Asteraceae, with a large flower head (inflorescence). The stem of the flower can grow up to 3 metres tall, with a flower head that can be 30 cm wide.

Birds and other animals enjoy eating sunflower seeds. Humans like to eat them too, although not all kinds, and often they are covered with chocolate, salt, or honey. Other types of sunflowers include the California Royal Sunflower, which has a burgundy (red + purple) flower head.

The sunflower is the state flower of Kansas. That is why Kansas is sometimes called the Sunflower State. To grow well, sunflowers need full sun. They grow best in fertile, wet, well-drained soil with a lot of mulch. In commercial planting, seeds are planted 45 cm (1.5 ft) apart and 2.5 cm (1 in) deep. Sunflower "whole seed" (fruit) are sold as a snack food, after roasting in ovens, with or without salt added. Sunflowers can be processed into a peanut butter alternative, Sunbutter. In Germany, it is mixed together with rye flour to make Sonnenblumenkernbrot (literally: sunflower whole seed bread), which is quite popular in German-speaking Europe. It is also sold as food for birds and can be used directly in cooking and salads. Sunflower oil, extracted from the seeds, is used for cooking, as a carrier oil and to produce margarine and biodiesel, as it is cheaper than olive oil. A range of sunflower varieties exist with differing fatty acid compositions; some 'high oleic' types contain a higher level of healthy monounsaturated fats in their oil than Olive oil.

Detail of disk florets. The cake remaining after the seeds have been processed for oil is used as a livestock feed. Some recently developed cultivars have drooping heads. These cultivars are less attractive to gardeners growing the flowers as ornamental plants, but appeal to farmers, because they reduce bird damage and losses from some plant diseases. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber. Traditionally, several Native American groups planted sunflowers on the north edges of their gardens as a "fourth sister" to the better known three sisters combination of corn, beans, and squash.[9] Annual species are often planted for their allelopathic properties.[citation needed] However, for commercial farmers growing commodity crops, the sunflower, like any other unwanted plant, is often considered a weed. Especially in the midwestern USA, wild (perennial) species are often found in corn and soybean fields and can have a negative impact on yields. Sunflowers may also be used to extract toxic ingredients from soil, such as lead, arsenic and uranium. They were used to remove uranium, cesium-137, and strontium-90 from soil after the Chernobyl disaster (see phytoremediation).

Look up Helianthus annuus in Wikispecies, a directory of species








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