Young Curly Brunette Girl In The Field Of Sunflowers

Sunflowers most commonly grow to heights between 1.5 and 3.5 m (5–12 ft). Scientific literature reports that a 12 m (40 ft), traditional, single-head, sunflower plant was grown in Padua in 1567. The same seed lot grew almost 8 m (26 ft) at other times and places, including Madrid. During the 20th century, heights over 8 m have been achieved in both Netherlands and Ontario, Canada.
Heliotropism
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.