Helianthus annuus

Description

The plant has an erect rough-hairy stem, reaching typical heights of 3 meters (9.8 ft). The tallest sunflower on record achieved 9.17 meters (30.1 ft). ^[2] Sunflower leaves are broad, coarsely toothed, rough and mostly alternate. What is often called ” flower ” of the sunflower is actually a ” flower head” or pseudanthium of numerous small individual-five-petaled flowers (” florets “). The outer flowers, which resembles petals, are called ray flowers . Each “petal” consists of a ligulecomposed of fused petal of an asymmetrical ray flower. They are sexually sterile and may be yellow, red, orange, or other colors. The flowers in the center of the head are called disk flowers . These mature into fruit (sunflower “seeds”). The disk flowers are arranged spirally. Generally, each floret is related to the next 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; however, in a very large sunflower head there could be 89 in one direction and 144 in the other. ^{[3] [4] [5]}This pattern produces the most efficient packing of seeds mathematically possible within the flower head. ^{[6] [7] [8]}

Most cultivars of sunflower are variants of Helianthus annuus , but other species (all perennials ) are also domesticated. This includes H. tuberosus , the Jerusalem Artichoke , which produces edible tubers.

Mathematical model of floret arrangement

A model for the pattern of florets in the head of a sunflower Was Proposed by H. Vogel in 1979. ^[9] This is Expressed in polar coordinates

{\ displaystyle r = c {\ sqrt {n}},}

{\ displaystyle \ 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 (55/144 of a circular angle, where 55 and 144 are Fibonacci numbers ) and gives a close packing of florets. This model has been used to produce computer graphics representations of sunflowers. ^[10]

Genome

The sunflower, Helianthus annuus , the genome is diploid with a base chromosome number of 17 and an Estimated genome size of 2871-3189 Mbp. ^[11] [12] Some sources claim its true size is around 3.5 billion base pairs (slightly larger than the human genome ). ^[13]

Cultivation and uses

To grow best, sunflowers need full sun. They grow best in fertile, moist, well- drained soil with heavy mulch . In commercial planting, seeds are planted 45 cm (1.48 ft) apart and 2.5 cm (0.98 in) deep. Sunflower “whole seed” are sold as a snack food, or after roasting in ovens, with or without salt and / or seasonings added. Sunflowers can be processed into a peanut butter alternative, sunflower butter . In Germany, it is mixed with rye flour to make Sonnenblumenkernbrot(literally: sunflower whole seed bread), which is quite popular in German-speaking Europe. It is also available for cooking and can be used directly in cooking and salads. Native Americans had multiple uses for sunflowers in the past, such as in bread, medical ointments, dyes and body paints. ^[14]

Sunflower halva is popular in Europe , including Belarus , Bulgaria , Romania , Moldova , Latvia , Lithuania , Estonia , Russia , Ukraine and other USSR countries. It is made of sunflower seeds instead of sesame .

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 monounsaturated fats in their oil than even olive oil .

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 , intended 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 for an alternative crop for producing nonallergenic rubber .

Traditionally, several Native American groups have planted sunflowers on the north edges of their gardens as a “fourth sister” to the three sisters combination of corn , beans , and squash . ^[15] Annual species are often planted for their allelopathic properties. ^[16]

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

Sunflowers can be used in phytoremediation to extract toxic ingredients from soil, such as lead, arsenic and uranium, and used in rhizofiltration to neutralize radionuclides and other toxic ingredients and harmful bacteria from water. They were used to remove caesium-137 and strontium-90 from a Chernobyl disaster , ^[17] and a similar event in the Fukushima Daiichi nuclear disaster . ^[18] [19]

Heliotropism misconception

A common misconception is that flowering sunflower heads the sun across the sky. Although immature flower buds exhibit this behavior, the mature flowering heads in a fixed (and typically easterly) direction throughout the day. ^[20] [21] This old misconception was disputed in 1597 by the English botanist John Gerard , who grew sunflowers in his famous herbal garden: “[some] reported to the sun, which I could never observe, although I have endeavored to find out the truth of it. ” ^[22] The uniform alignment of sunflower heads in a field might give some people the impression that the flowers are tracking the sun.

This alignment results from heliotropism in an earlier development stage, the bud stage, before the appearance of flower heads ( anthesis ). ^[23] The buds are heliotropic until the end of the bud stage, and finally face East. ^[24] [25] Their apparent heliotropic motion is a circadian rhythm, synchronized by the sun, which continues if the sun disappears on cloudy days or if plants are moved to constant light. ^[26] If a sunflower plant in the bud is rotated 180 °, the bud will be turned away from the sun for a few days, as resynchronization by the sun takes time. ^[27]The heliotropic motion of the bud is caused by a growing growth of the flower stalk and only occurs before the open flowers. The motion of the ‘nodding’ buds is irreversible, cumulative goal. When growing of the flower stalk stops and the flower is mature, the heliotropisms also stops and the flower faces east from that onward moment. This eastward orientation allows rapid warming in the morning and, as a result, an increase in pollinator visits. ^[26] Sunflowers do not have a pulvinus below their inflorescence. A pulvinus is a flexible segment in the leaf stalks (petiole) of some plant species and functions as a ‘joint’. It effectuates leaf motion due to reversible exchange in turgorpressure, which occurs without growth. The sensitive plant ‘s closing leaves are a good example of reversible leaf movement via pulvinuli.

History

Although it was commonly accepted that the sunflower was first used in the US, about 5000 years ago, ^[28] there is evidence that it was first domesticated in Mexico ^[29] around 2600 BC. These were found in Tabasco, Mexico at the San Andres dig site. The earliest known examples in the United States of a fully domesticated sunflower have been found in Tennessee, and date to around 2300 BC. ^[30] Many Indigenous peoples used the sunflower as the symbol of their solarity , including the Aztecs and the Otomi of Mexico and the Incasin South America. In 1510 early Spanish explorers Encountered the sunflower in the Americas. ^[31] Of the four plants-have-been Known to domesticated in what is now the eastern continental United States ^[32]and to Have Become major agricultural commodities, the sunflower is Currently The Most economically significant.

During the 18th century, the use of sunflower oil became very popular in Russia, particularly with members of the Russian Orthodox Church, because it was one of the few that was allowed during Lent , according to some fasting traditions . ^[33] In the early 19th century it was first commercialized in the village of Alexeyevka in Voronezh Governorate by the merchant named Daniil Bokaryov, who developed a technology for its large-scale extraction, and quickly spread around. The town’s coat of arms includes an image of a sunflower ever since.

Among the Zuni people , the fresh or dry root is being chewed by the doctor . ^[34] This compound is of the root is applied with much ceremony to rattlesnake bites. ^[35] Blossoms are also used ceremonially for anthropic worship. ^[36]

Culture

• The sunflower is the state flower of the US state of Kansas , and one of the city flowers of Kitakyushu , Japan .
• The sunflower is often used as a symbol of green ideology . The sunflower is also the symbol of the Vegan Society .
• During the late 19th century, the flower was used as the symbol of the Aesthetic Movement .
• The flowers Were the subject of Van Gogh ‘s Sunflowers series of paintings .
• The sunflower is the national flower of Ukraine .
• The sunflower was chosen as the symbol of the Spiritualist Church for many reasons, but mostly because it turns towards the sun as “Spiritualism turns toward the light of truth”. As stated earlier in the article, this is in fact, not true. Modern Spiritualists often have art or jewelry with sunflower designs. ^[37]
• Sunflowers were also worshipped by the Incas because they viewed it as a symbol for the Sun. ^[38]
• The sunflower is the symbol behind the Sunflower Movement , a 2014 mass protest in Taiwan .

Cultivars

The Following are cultivars of sunflowers (Those marked agm -have Gained the Royal Horticultural Society ‘s Award of Garden Merit ): –

Other species

There are many species in the sunflower genus Helianthus , and many species in other genera that may be called sunflowers.

• The Maximillian sunflower ( Helianthus maximiliani ) is one of 38 species of native perennial sunflower to North America . The Land Institute and other breeding programs are currently exploring the potential for these as a perennial seed crop.
• The sunchoke ( 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 .

Sunflower hybrids

In today’s market, most of the sunflower seeds or hybrids. Hybrids or hybridized sunflowers are produced by crossbreeding different types and species of sunflowers, for example crossbreeding cultivated sunflowers with wild species of sunflowers. By doing so, new genetic recombinations are finally obtained to produce new hybrid species. These hybrid species have a higher fitness and carry properties or characteristics that farmers look for, such as resistance to pathogens. ^[46]

Threats and diseases

One of the major threats that sunflowers face today is Fusarium , a filamentous fungi that is found largely in soil and plants. It is a pathogen that increases the incidence of sunflower and other diseases. ^[46]

Downy mildew is another disease to which sunflowers are susceptible. Its susceptibility to downy mildew is particular to the sunflower’s way of growth and development. Sunflower seeds are generally planted only in deep ground. When such shallow planting is done in the soil and soaked earth or soil, it increases the chances of such diseases as downy mildew.

Another major threat to sunflower is broomrape , a parasite that attacks the root of the sunflower and causes extensive damage to sunflower crops, as high as 100 percent. ^[47]

See also

• International Sunflower Guerrilla Gardening Day
• List of sunflower diseases

References

Footnotes