Advances in Agronomy 1 : Research Advances in Sunflower

Advances in Agronomy 1 : Research Advances in Sunflower
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Advances in Agronomy 1 : Research Advances in Sunflower

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Publisher: Agrobios Publications
ISBN: 9788190430920
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Preface Sunflower Helianthus annuus L. is one of the few crop species that originated in North America most originated in the fertile crescent, Asia or South or Central America . It was probably a camp follower of several of the western native American tribes who domesticated the crop possibly 1000 BC and then carried it eastward and southward of North America. The first Europeans observed sunflower cultivated in many places from southern Canada to Mexico. Sunflower was probably first introduced to Europe through Spain, and spread through Europe as a curiosity until it reached Russia where it was readily adapted. Selection for high oil in Russia began in 1860 and was largely responsible for increasing oil content from 28 to almost 50 . The high-oil lines from Russia were reintroduced into the U.S. after World War II, which rekindled interest in the crop. However, it was the discovery of the male-sterile and restorer gene system that made hybrids feasible and increased commercial interest in the crop. Production of sunflowers subsequently rose dramatically in the Great Plains states as marketers found new niches for the seeds as an oil crop, a birdseed crop, and as a human snack food. Production in these regions in the 1980s has declined mostly because of low prices, but also due to disease, insect and bird problems. Sunflower acreage is now moving westward into dryer regions however, 85 of the North American sunflower seed is still produced in North and South Dakota and Minnesota. The name Helianthus, being derived from helios the sun and anthos a flower , has the same meaning as the English name Sunflower, which it is popularly supposed has been given these flowers from a supposition that they follow the sun by day, always turning towards its direct rays. In Peru, this flower was much reverenced by the Aztecs, and in their temples of the Sun, the priestesses were crowned with Sunflowers and carried them in their hands. The early Spanish conquerors found in these temples numerous representations of the Sunflower wrought in pure gold. Plants are tall, hardy, annual or perennial herbs, several of which are grown in gardens, being of easy cultivation in moderately good soil, and that useful plant of the kitchen garden, the Jerusalem Artichoke Helianthus tuberosus , is also a member of the genus. It is an annual herb, with a rough, hairy stem, 3 to 12 feet high, broad, coarsely toothed, rough leaves, 3 to 12 inches long, and circular heads of flowers, 3 to 6 inches wide in wild specimens and often a foot or more in cultivation. Sunflower leaves are phototropic and will follow the sun's rays with a lag of 120 behind the sun's azimuth. This property has been shown to increase light interception and possibly photosynthesis.
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. The flowerheads are composed of many small tubular flowers arranged compactly on a flattish disk those in the outer row have long strap-shaped corollas, forming the rays of the composite flower. 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