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Tuesday, October 8, 2013

Helianthus annuus Flowers

Type of Flowers
Helianthus annuus:
The Helianthus annuus ( sunflower ) is an annual plant native to the Americas. It possesses a large inflorescence (flowering head), and its name is derived from the flower's shape and image, which is often used to depict the sun. The plant has a rough, hairy stem, broad, coarsely toothed, rough leaves, and circular flower heads. 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 fibre which may be used in paper production.

The root of a sunflower reflects its characteristic of being a dicot. Out of the seed, the first root, radicle, pushes through and develops into a taproot. It continues to expand through primary and secondary tissues. Primary roots develop from primary tissues of the apical trimester that increase the length of the plant. Secondary roots, from secondary tissues of the lateral trimesters give rise to the girth of the plant. Both structures are vital for the growth and strength of the stem. 
The stem of a sunflower grows from the plume found inside the seed. The plumule is an embryo shoot with a hypocaust stem structure below the point where the plume was attached and an epicycloid stem structure above this attachment point.Sincej a sunflower is a divot, thea cross-section ofm a stem organizese the vascular bundles in an away to separate the cortex and create a pith. This is opposite of its root structure which does not includes a pith. The vascular bundles consisting of xylem and phloem transport water, mainly acquired from the roots, and food, mainly developed in the leaves, throughout the plant. 
The leaf of a sunflower is considered a simple leaf, being one which consists of a single blade.The plumule gives rise to the first leaves of the plant that will go on to grow into organs for transpiration, with the opening and closing of the stomata found within the cell structure of leaves; for photosynthesis, and for other metabolic activities.As far as structure, a sunflower blade is heart-shaped, has pinnate venation, and alternates along the stem. Its green color accents the vibrant green or other variety of leaves the flower has. The flower of a sunflower is actually several flowers, which is why it is considered an inflorescence. An inflorescence is a group of several flowers.Therefore, the many individual packets at the center of the head are the fruits of the plant, not the seeds. Each flower of the sunflower consists of the typical structures of a flower: receptacle, peduncle, sepal, petals, stamen, and a pistil. Consequently, every flower is able to develop fruit, or the ripened ovary, with the ovule (seed) inside.

What is usually called the "flower" on a mature sunflower is actually a "flower head" (also known as a "composite flower") of numerous florets (small flowers) crowded together. The outer petal-bearing florets (ray florets) are sterile and can be yellow, red, orange, or other colors. The florets inside the circular head are called disc florets, which mature into seeds The flower petals within the sunflower's cluster are always in a spiral pattern. Generally, 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 commonly grow to heights between 1.5 and 3.5 m (5–12 ft.). The tallest sunflower confirmed by Guinness World Records is 8.0 m (2009, Germany). In 16th-century Europe the record was already 7.3 m (24 ft., Spain).Most cultivars are variants of H. annuus, but four other species (all perennials) are also domesticated. This includes H. tuberosus, the Jerusalem Artichoke, which produces edible tubers.

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