The Orchids are one of the most exquisite and fascinating flowers in the world. In fact, so fascinated is the world with the Orchids that many countries have adopted different varieties of orchids as their respective National Flowers. Orchids are proliferated across most countries. The orchid flowers are especially prolific in the tropics, where the majority of the species grow on the trunks and branches of trees. In the temperate zones, such as southern Australia, most Orchids grow on the ground.
In 1735, Carl Von Lin (Linnaeus), a Swedish botanist, used the word Orchidaceae (taken from Orkhis), which led to further discoveries carried on by Darwin. Orchids belong the the family Orchidaceae. There are 2 different growth types of Orchids. Generally Orchids are divided into Monopodial, Sympodial varieties. Monopodial Orchids have a central stem of growth. Monopodial Orchids have no pseudobulbs, but produce new growth from the crown of the plant. Flowers are produced from the stem between the leaves, usually alternately from side to side.
Sympodial Orchids possess a rhizome, which sends out a shoot. This develops into a stem and leaves and eventually produces flowers. Later, from the base of this growth, a new shoot develops and goes on. The buds are often protected by a sheath.
Depending on their growth habits, Orchids are generally divided into three main categories-
· Epiphytic Orchids are grown perched high in the trees clinging to branches or in the trunk apex of the tree. They derive their nutrients from the air, rain, and any decaying vegetation, which the roots can contact. Epiphytic Orchids have specialised aerial roots, which have a white spongy layer of cells called velamen. This protects the inner root tissues and absorbs water. These roots will also often dangle free in the atmosphere.
· Lithophytic Orchids are seen covering the bases and forks of trees or filling crevices in rocks, and absorb a maximum supply of nutrients from decaying mosses.
· Terrestrial Orchids are seen under the ground, having a symbiotic relation with a special fungus, which in turn supports the orchid with the essential nutrients.
· Orchids have the largest variety of flowering plants with an estimated of 20,000 to 30,000 naturally occurring species .
· Orchids are seen growing in all the continents except Antarctica.
· In 1856, the first man made Orchid was cultivated.
· There are 2 species of Orchids growing in Australia and 3 species in the Arctic circle, growing underground plants with their flowers shooting up above the soil.
· In order to achieve pollination, some Orchids of the genus Ophrys (called bee Orchids) bear flowers resembling female insects in appearance and smell. Male insects are attracted to the flowers and attempt to mate with them, thus pollinating the flowers.
· The bloom time or the life of an Orchid depends upon the type of Orchid in bloom.
· Phalaenopsis are among the easiest and most rewarding Orchids to grow.
· The Orchid genus, Vanilla, is commercially important, and is used as a foodstuff in flavoring as the vanilla essence.
· Orchids are among the most highly prized of ornamental plants.
· There are many variations in the structure and the color of an Orchid flower. Some Orchids have one flower on a stem, and other Orchids have more than a hundred together on a single spike. In color variations, African Orchids are white, while Asian orchids are often multicolored.
· A typical orchid flower is zygomorphic, i.e., bilaterally symmetric, with exceptions like the genera Mormodes, Ludisia and Macodes. The Orchid flowers growing on racemes or panicles can be: basal i.e. produced from the base of the pseudobulb, as in the Cymbidium; apical i.e., produced from the apex of the orchid, as in Cattleya; or axillary i.e., coming from a node between the leaf axil and the plant axis as in Vanda.
· The basic Orchid flower is composed of three sepals in the outer whorl, and three petals in the inner whorl. The medial petal is usually modified and enlarged (then called the labellum or lip), forming a platform for pollinators near the center of the corolla. Together, except the lip, they are called tepals. Sepals form the exterior of the bud. They are green in this stage, but sometimes, if the Orchid blossom is, for example, Purple, the buds can show a purple tint.
· The reproductive organs of an Orchid are in the center (stamens and pistil), and have adapted to become a cylindrical structure called the column or gynandrium. On top of the column lies the stigma, the vestiges of stamens and the pollinia, a mass of waxy pollen on filaments. These filaments can be a caudicle (as in Habenaria) or a stipe (as in Vanda). These filaments hold the pollinia to the viscidium (sticky pad).
· The pollen are held together by the alkaloid viscine. This viscidium adheres to the body of a visiting insect. The type of pollinia is useful in determining the genus. On top of the pollinia is the anther cap, preventing self-pollination. At the upper edge of the stigma of single-anthered orchids, in front of the anther cap, is the rostellum, a slender beaklike extension.
· The Orchid ovary is always inferior (located behind the flower), three-carpelate and one or three-partitioned, with parietal placentation with few exceptions. If pollination succeeds, the sepals and petals fade and wilt but they remain attached to the ovary.