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Sunflower

2007 Schools Wikipedia Selection. Related subjects: Plants

        How to read a taxoboxSunflower
           Scientific classification

   Kingdom: Plantae
   Class:   Magnoliopsida
   Order:   Asterales
   Family:  Asteraceae
   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 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.

Description

   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.
   Sunflower head displaying florets in spirals of 34 and 55 around the
   outside
   Sunflower head displaying florets in spirals of 34 and 55 around the
   outside

   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.

   The disc florets mature into what are traditionally called " sunflower
   seeds", but are actually the fruit (an achene) of the plant. The true
   seeds are encased in an inedible husk.

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 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 colour.

   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

   A sunflower farm near Mysore, India.
   A sunflower farm near Mysore, India.
   Sunflower heads solds as snacks in China.
   Sunflower heads solds as snacks in China.

   Sunflowers are native to the Americas. The earliest known examples of a
   fully domesticated sunflower were found at the Olmec site of San Andrés
   dating some time before 2500 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.

   The Giant sunflower (Helianthus giganteus) is native to Connecticut.
   They can grow to be between 3 and 12 feet tall. Their flower heads can
   be between 2 to 3 inches wide. They are most commonly found in valleys
   with wet meadows or swamps. The Giant sunflower grows between July and
   October.

   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') apart and 2.5 cm (1") deep.

   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.

   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.

   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.

Diseases

Greek myth

   In Greek mythology, a girl named Clytie fell in love with the sun god
   Apollo, and would do nothing but watch his chariot move across the sky.
   After nine days, she was transformed into a sunflower. However, the
   word "sunflower" and its cognates existed long before Helianthus annuus
   was brought to Europe, and it is thought that the myth (which is
   mentioned in Ovid's poem Metamorphoses) actually refers to heliotrope.

Trivia

     * 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.

Flower formation

   1. The first stage of the flower formation

   2. The flower is still covered, but faces the sun

   3. The flower is nearly completely exposed

   4. The flower is completely exposed

     * Video: Sunflower opening  — Watch in browser
          + Time lapse video of a sunflower opening over an 8.75 hour
            period.

Gallery

   Sunflowers in Manila, Philippines

   Sunflowers

   Bumble bee sampling Sunflower nectar

   Sunflowers growing near Fargo, North Dakota

   Lone sunflower about 2 m (6 ft, 6') tall

   Sunflower seedlings, just three days after germination

   Sunflower field in Eastern Bulgaria

   Sunflower Profile

   Sunflower and pollinator

   Sunflower (French:Tournesol) from MediaWiki logo

   Large Russian Sunflower

   Sunflower

   The Netherlands, June 2006

   A field of Sunflowers in the Canton de Genève in Switzerland

   Fruiting head

   Sunflower seeds in many variations and sizes.

   Sunflower close-up.

   Retrieved from " http://en.wikipedia.org/wiki/Sunflower"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
