Young Curly Brunette Girl In The Field Of Sunflowers

Sun flowers have a type phototropic response called heliotropism (sun turning); the leaves and flower heads young sunflowers follow the sun and their orientation therefore changes from east to west during the day. The movements become a circadian response and when plants are rotated 180 degrees, the old response pattern is still followed for a few days, with leaf orientation changing from west to east instead. The leaf and flower bud phototropism occurs while the leaf petioles and stems are still actively growing and once mature the movements stop. The movement occurs as the petioles bend or twist during the day and at night they unbend or untwist.
History
The sunflower is native to the Central Americas. The evidence thus far is that it was first domesticated in Mesoamerica, present day Mexico, by at least 2600 BC. It may have been domesticated a second time in the middle Mississippi Valley, or been introduced there from Mexico at an early date, as maize was. The earliest known examples a fully domesticated sunflower north Mexico have been found in Tennessee and date to around 2300 BC. Many indigenous American peoples used the sunflower as the symbol their solar deity, including the Aztecs and the Otomi Mexico and the Incas in South America. Francisco Pizarro was the first European to encounter the sunflower in Tahuantinsuyo, Peru. Gold images the flower, as well as seeds, were taken back to Spain early in the 16th century. Some researchers argue that the Spaniards tried to suppress cultivation the sunflower because its association with solar religion and warfare.