The Orchidaceae

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The Orchidaceae

  1. 1. The Orchidaceae By Anna Selivanova
  2. 2. THE ORCHIDACEAE The Orchidaceae is a morphologically diverse and widespread family of monocots in the order Asparagales. It is one of the two largest families of flowering plants. The number of orchid species equals more than twice the number of bird species, and about four times the number of mammal species. It also encompasses about 6–11% of all seed plants. Since the introduction of tropical species in the 19th century, horticulturists have produced more than 100,000 hybrids and cultivars.
  3. 3. The name comes from the Greek ὄρχις (órkhis), literally meaning "testicle", because of the shape of the root. Orchid was introduced in 1845 by John Lindley in School Botany, due to an incorrect attempt to extract the Latin stem from Orchidaceae. The Greek myth of Orchis explains the origin of the plants. Orchis, the son of a nymph and a satyr, came upon a festival of Dionysios in the forest. He drank too much, and attempted to rape a priestess of Dionysios. For his insult, he was torn apart by the Bacchanalians. His father prayed for him to be restored, but the gods instead changed him into a flower. These flowers were previously called Orchis, Satyrion, or "ballockwort".
  4. 4. Orchidaceae are cosmopolitan, occurring in almost every habitat apart from glaciers. The world's richest concentration of orchid varieties is found in the tropics, mostly Asia, South America and Central America, but they are also found above the Arctic Circle, in southern Patagonia, and even two species of Nematoceras on Macquarie Island, close to Antarctica. Orchids are easily distinguished from other plants, as they share some very evident apomorphies. Among these are: bilateral symmetry, many resupinate flowers, a nearly always highly modified petal, fused stamens and carpels, and extremely small seeds.
  5. 5. Terrestrial orchids may be rhizomatous or form corms or tubers. The root caps of terrestrials are smooth and white. Epiphytic orchids have modified aerial roots that can sometimes be a few meters long. In the older parts of the roots has the function to absorb humidity. It is made of dead cells and can have a silvery-grey, white or brown appearance.
  6. 6. Orchidaceae are well known for the many structural variations in their flowers. Some orchids have single flowers, but most have a racemose inflorescence, sometimes with a large number of flowers. Orchid flowers with abnormal numbers of petals or lips are called peloric. Peloria is a genetic trait, but its expression is environmentally influenced and may appear random.
  7. 7. The complex mechanisms which orchids have evolved to achieve cross-pollination were investigated by Charles Darwin and described in his 1862 book Fertilisation of Orchids. Orchids have developed highly specialized pollination systems, thus the chances of being pollinated are often scarce, so orchid flowers usually remain receptive for very long periods, and most orchids deliver pollen in a single mass. Each time pollination succeeds, thousands of ovules can be fertilized. Some orchids mainly or totally rely on self-pollination, especially in colder regions where pollinators are particularly rare.
  8. 8. A study has hypothesized that the origin of orchids goes back much longer than originally expected. Indicates orchids may have arisen 76 to 84 million years ago during the Late Cretaceous. In other words, they may have coexisted with dinosaurs. It also shows insects were active pollinators of orchids then.
  9. 9. The leaves of some orchids are considered ornamental. They show a sparkling silver and gold veining on a light green background. The attractive mottle of the leaves of lady's slippers from tropical and subtropical Asia, is caused by uneven distribution of chlorophyll.
  10. 10. The scent of orchids is frequently analysed by perfumers to identify potential fragrance chemicals. The other important use of orchids is their cultivation for the enjoyment of the flowers. Most cultivated orchids are tropical or subtropical, but quite a few which grow in colder climates can be found on the market.

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