A helianthus (Helianthus annuus) is an annual plant in the Family Asteraceae with a big flower head (inflorescence). A stem of the flower might develop as much as Trio metres tall, with a flower head reaching 30cm from side to side. A helianthus is notable for turning to face a Sun, a behavior called heliotropism.

History
Helianthus come indigene to the Americas, and were domestic about Yard B.C. Francisco Pizarro found the Inca subjects venerating the helianthus as an image of their sun god, and gold images of the "flower" when well as seeds were taken back to Europe early in the 16th century. Sunflower is from either a Greek for "sunflower". Within French, it is known as "tournesol", & around Italian, "girasole".

Greek myth

Inside Greek myth, a girl known as Clytie fell in love by having a sun god Apollo, and would clean nothing however watch over his chariot move across a sky. Fallowing nine years, she was transformed into the helianthus. Notwithstanding, a word "sunflower" & its cognates existed long prior to Helianthus annuus was bring back Europe, and these are thought that a myth (which is mentioned around Ovid's poem Metamorphoses) actually refers to the marigold.

Description
A term "sunflower" is too wont to refer to a lot plants of the genus Helianthus, numbers of of which are then perennial plants.

What is known as a flower is actually a head (formerly composite flower) of many flowers crowd. A outer flowers come a ray florets & may be yellow, maroon, orange, or more colors. These flowers come unfertile. A flowers that fill a round head in a ray floret come known as disc florets. A arrangement of florets in this bunch is usually such that every is separated from either a next by around a golden angle, producing a pattern of spirals where a total of left spirals & the total of perfect spirals come consecutive Fibonacci numbers. A disc florets mature into "seeds". Notwithstanding, what you ordinarily call for a seeds come actually a fruit (an achene) of a plant, with the admittedly seeds encased within an uneatable shell.

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Heliotropism
Sunflower seedlings, just three days after germination Virtually all flowerheads in a field of flaming helianthus come turned towards a east, in which a sun rises both morning (hence the helianthus's Spanish name girasol, and its French name tournesol). Unformed helianthus in the bud stage exhibit heliotropism; in sunny times a bud tracks a sun on its journeying along a sky from either east to west, when when asleep or even at dawn it comes back to its eastbound orientation. a motion is performed by drive cells in the pulvinus, a flexible section of the stem upright in the image below the bud. A stem stiffens at a prevent of a bud stage, & after a bloody stage is reached the stem freezes around its eastbound counsel. So, bloody helianthus come non heliotropic any longer, possibly though virtually all flowerheads are facing a counsel in which a sun rises.

Cultivation and Uses
To develop swell, helianthus want to the full sun. It develop better inside fertile, dampish, easily-drained soil with a lot of mulch. Seeds should exist as 45 cm (Unity.Fin') apart & implanted Deuce.V cm (Single") deep.

Sunflower "wholly seeds" (fruit) are sold as snacks, especially in the United States and Europe, and as food for birds. Sunflower oil, extracted from the seeds, is used for cooking (but is less cardiohealthy than olive oil), as a carrier oil and is used to produce biodiesel, for which it is less expensive than the olive product. 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. There are also new breeds of sunflowers which are transgenic, so that they are resistant to some diseases. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.

The sunflower is the state flower of the U.S. state of Kansas, and one of the city flowers of Kitakyushu, Japan.

The Jerusalem artichoke (Helianthus tuberosa) is related to the sunflower. The Mexican sunflower is Tithonia rotundifolia. False sunflower refers to plants of the genus Heliopsis.

Scientific literature reports, from 1567, that a 12 m (40'), traditional, single-head, sunflower plant was grown in Padua. The same seed lot grew almost 8 m (24') at other times and places (e.g. Madrid). Much more recent feats (past score years) of over 8 m (25') have been achieved in both Netherlands and Canada (Ontario). Flower formation
Image:Sunflower opening 1-KayEss-2.jpeg|1. The first stage of the flower formation Image:Sunflower opening 2-KayEss-2.jpeg|2. The flower is still covered, but faces the sun Image:Sunflower opening 3-KayEss-1.jpeg|3. The flower is nearly completely exposed Image:Sunflower opening 4-KayEss-2.jpeg|4. The flower is completely exposed Mathematical Properties

Sunflower heads contain seeds in spiral patterns. There will be one family of spirals that goes clockwise and another family of spirals that interlaces between these, going anti-clockwise. Counting the number of spirals in each family will reveal each to be a Fibonacci number, typically 34 in one direction and 55 in the other; on a very large sunflower you may see 89 in one direction and 144 in the other.