Sun Flowers from Wikipedia
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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 the flower head reaching 30 cm in diameter. The term “sunflower” is also used to refer to all plants of the genus Helianthus, many of which are perennial plants.
What is usually called the flower is actually a head (formally composite flower) of numerous flowers (florets) crowded together. The outer flowers are the ray florets and can be yellow, maroon, orange, or other colors, and are sterile. The florets inside the circular head are called disc florets.
The florets within this cluster are arranged spirally. Typically each floret is oriented toward the next by approximately the golden angle, 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 1 direction and 55 in the other; on a very large sunflower you may see 89 in one direction and 144 in the other.
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 move to track 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 the blooming stage are not heliotropic anymore. The stem has frozen, typically in an eastward orientation. 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.
Cultivation and uses
Sunflowers are native to the Americas, and were domesticated around 1000 B.C. The Incas used the sunflower as an image of their sun god. Gold images of the flower, as well as seeds, were taken back to Europe early in the 16th century.
Sunflower “whole seed” (fruit) is sold as snacks and can be processed into a peanut butter alternative, Sunbutter, especially in China, the United States, the Middle East and Europe. In Russia it is probably the most wide spread snack. 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 (but is less cardiohealthy than olive oil), as a carrier oil and 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. Additionally, the stem of a dead sunflower can dry out open wounds.
For farmers not intending to grow it, the sunflower is considered a noxious weed. The wild variety will grow unwanted in corn and soybean fields which can have a negative impact on yields.
- 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).
- The sunflower is often used as a symbol of green ideology, much as the red rose is a symbol of socialism or social democracy