Sunflower

Description:

...an annual plant native to the Americas. It possesses a large inflorescence (flowering head). The sunflower is named after its huge, fiery blooms, whose shape and image are often used to depict the sun. It has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads of flowers. The heads consist of many individual flowers which mature into seeds, often in the hundreds, on a receptacle base. From the Americas, sunflower seeds were brought to Europe in the 16th century, where, along with sunflower oil, they became a widespread cooking ingredient. Leaves of the sunflower can be used as cattle feed, while the stems contain a fiber which may be used in paper production.

Habitat:

The evidence thus far is that the sunflower was first domesticated in what is now the southeastern US, roughly 5000 years ago., and possibly introduced into Mexico at an early date, as other crops such as maize were exchanged. The earliest known examples of a fully domesticated sunflower have been found in Tennessee, and date to around 2300 BC[citation needed]. 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. In 1510 early Spanish explorers encountered the sunflower in the Americas and carried its seeds back to Europe. Of the four plants known to have been domesticated in what is now the continental United States to have become an important agricultural commodity, sunflower is currently the most economically important. During the 18th century, the use of sunflower oil became very popular in Russia, particularly with members of the Russian Orthodox Church, because sunflower oil was one of the few oils that was allowed during Lent, according to some fasting traditions.

Notes:

A common misconception is that sunflower heads track the Sun across the sky. This old and chronic misconception was debunked already in 1597 by the English botanist John Gerard, who grew sunflowers in his famous herbal garden: "[some] have reported it to turn with the Sun, the which I could never observe, although I have endeavored to find out the truth of it." The uniform alignment of sunflower heads in a field might give some people the false impression that they are tracking the sun, but the heads are actually pointing in a fixed direction (East) all day long. However, the uniform alignment does result from heliotropism in an earlier development stage, the bud stage, before the appearance of flower heads (anthesis). The buds are heliotropic until the end of the bud stage, and finally face East. That is why blooming (and faded) flowers of the sunflower are living compasses (however not too exact): West is behind, North to the left, and South to the right. This is true for open space only . Their heliotropic motion is a circadian rhythm, synchronized by the sun, which continues if the sun disappears on cloudy days. If a sunflower plant in the bud stage is rotated 180°, the bud will be turning away from the sun for a few days, as resynchronization by the sun takes time . The heliotropic motion of the bud is performed by the pulvinus, a flexible segment just below the bud, due to reversible changes in turgor pressure (no growth).