Projekty & aktivity
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04.09.2011
Slnečné letoSlnečné leto praje najmä slnečniciam. Ich žiarivo žltá farba napovedá, že sú hodné svojho mena.| Počet komentárov [ 2 ]
"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 of over 8 m have been achieved in both Netherlands and Ontario, Canada."
http://www.pfaf.org/user/default.aspx Archaeologists have recovered remains of sunflower seeds dating back to the year 800 AD. Sunflower (Helianthus annuus) is an annual plant native to the Americas that possess a large inflorescence (flowering head). The sunflower got its name from its huge fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads of flowers. The heads consist of 1,000-2,000 individual flowers joined together by a receptacle base. Sunflower seeds were taken to Europe in the 16th century where, along with sunflower oil, they became a wide-spread cooking ingredient. Sunflower leaves can be used as a cattle food, while the stems contain a fibre which may be used in paper production. The florets within the sunflower's cluster are arranged in a spiral pattern. Typically each floret is oriented toward the next by approximately the golden angle, 137.5°, 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 one direction and 55 in the other; on a very large sunflower there could be 89 in one direction and 144 in the other. This pattern produces the most efficient packing of seeds within the flower head. 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 of over 8 m have been achieved in both Netherlands and Ontario, Canada Despite the common belief, mature sunflowers do not track the sun. The mature flowerheads typically face east; only young sunflowers exhibit heliotropism (sun turning): the leaves and buds of young sunflowers follow the sun so that their orientation changes from east to west during the course of a day.
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