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ORCHIDS, the most beautiful flowers in god's creation, comprise a unique group of plants. Taxonomically, they represent the most highly evolved family among monocotyledons with 600-800 genera and 25,000-35,000 species . Orchids exhibit an incredible range of diversity in size, shape and colour of their flowers. They are most pampered of the plants and occupy top position among all the flowering plants valued for cut flower production and as potted plants. They are known for their longer lasting and bewitchingly beautiful flowers which fetch a very high price in the international market. Theophrastus, who is also called the father of botany (370-285 BC), gave the name "ORCHIDS" to the group of bizarre plants on the basis of the resemblance of paired underground tubers of these plants to masculine anatomy (the testes). This resemblance was also responsible for the mistaken belief that the orchids posses aphrodisiac properties and eating of underground tubers might "provoke venus" and they may beget male children

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In the Indian Vedic scriptures there is a mention of the plants under the name "VANDA", which has been adapted as a generic name in one of the most beautiful group of orchids. Most of the orchids are perennial herbs with simple leaves. Although the specialized flower structure conforms to a standard plan, the vegetative parts are shown great variation, a large number of them being epiphytes, or terrestrial and a few saprophytes and leafless in nature. Majority of the cultivated orchids are native of tropical countries and occur in their greatest diversity in humid tropical forest of South and Central America, Mexico, India, Ceylon, Burma, South China, Thailand, Malaysia, Philippines, New Guinea and Australia. Brazilian cattleyas, Mexican laelias and Indian dendrobiums, cymbidiums and vandas have played a major role in the development of modern orchid industry in the world.

The evolution of orchid culture from hobbyist to commercial grower was very slow as most of the orchids collected from different regions did not adapt to local conditions and died. The methods of propagation were not known and most of the orchids which flowered under utmost care were found to be self sterile. Further, it was difficult to germinate the seeds, which lacks any functional endosperm. The seeds sown in the nursery beds required long period of germination and any disturbance to the soil or physical environment destroyed the whole population.

It was only in 1821 when Conrad Loddiges and sons started growing orchid plants commercially at their nursery in Hackney, followed by John Daminy of M/s Veitch & Sons who produced the first orchid hybrid between two Calanthe species in 1852, which flowered in 1856 in Veitch Nursery Exeter, England . This was followed by a large number of man made hybrids produced by hobbyists and small growers. In 1913, Sun Kee Nursery, Singapore, started the first cut-flower production of Arachnis type hybrids.

The major developments in cultivation of orchids in the world have been due to modern scientific technology which has been suitably used in case of orchid seed germination and meristem culture. Today orchids are grown on assembly-line method in extensive glasshouses with controlled environment and the sale of orchid flowers runs in millions of dollars. The modern methods of propagation have bought orchid cultivation on par with other commercial crops.

Orchids in nature grow protected from the tropical sun by the shades of trees. Under controlled condition the orchids can be grown in specially designed orchidaria or orchid houses, running North and South and made from materials like split bamboo, glass, shadenets, etc. A central tank filled with water or by using artificial fogging nozzles helps in increasing humidity .However, it must be clear that all types of orchids cannot be grown under one roof. While tropical orchid enjoy humid, warm atmosphere and burst into activity during rainy season, temperate orchid should be growing in cool houses. Orchids dislike sudden change in temperature, however a difference of 10 C - 20 C between day and night temperature is beneficial. The best suitable range is 18 C to 30 C, proper ventilation is must to provide fresh air and also helps in reducing the temperature.

Indirect sunlight is ideal for orchids. Seedlings requires less than adult plants. Very poor light tends to produce weak plants and retards flowering. A plant which has been grown in shades should be gradually be shifted to sunlight conditions. The optimum requirement of light varies between species to species. Cypripedium and Phalaenopsis require only 200-300 foot candles. Whereas genera like Vanda and Aranda thrive best under 800 foot-candles. Majority of orchids are day neutral and are not influenced by day length. But in Cattleya both short-day and long-day plants are met with. Usually in the growing areas of Thailand,Malaysia and Singapore growers have used shadenets in 35% to 85% shade percentage to grow orchids of different genera.

Humid warm atmosphere is most essential for the growth of most of the tropical orchids, which do not have well established root system. It is a good idea to have a water tank or pool in the center of the orchidaria to maintain humidity, which should not be less than 30% at night and 80% during day time, The plants should be watered 2-3 times a day and should not be allowed to dry up during hot climate. Plants in active growth require more water. Similarly plants in baskets require more water than those in pots. Care should be taken to water the plants with a fine spray by using standard nozzles and not to hit the plants with powerful jets of water. Plants which are freshly potted should be watered very sparingly till the new roots appear and watering should be gradually increased.

Orchids should be potted in small container/spots according to the size of the plants. As a thumb rule, orchids should be under potted to get more flowers. Any kind of pot/container which can hold medium and provide aeration is suitable. Most of the people prefer plastic pots which retain moisture longer than mud pots. Vandaceous and Sarcenthene orchids can be grown in teak-wood baskets. Orchid plants should not be disturbed frequently and repotting done only when absolutely necessary.
Orchids like Cymbidium, react favourably when repotted after 2-3 years whereas Vandeceous orchids and Paphiopedilum should not be disturbed unless very necessary.

Terrestrial orchids, like Spathoglottis, Phaius and Calanthe, should be grown in 20-25 cm pots with 1:1:1 mixture of leaf mould, FYM and sand. For Paphiopedilum A mixture of 2 parts leaf mould, 2 parts loam soil and 1 part each of brick pieces and charcoal is recommended. Experiments conducted at Botanical Survey Of India, Calcutta, have revealed that in case of Rhychostylis gigantea, chunks of hard-wood charcoal alone as potting substance were superior then eleven other potting media. Tree fern fiber also performed better than the other media while coconut husk and over-burnt brick as planting substance had adverse effects on growth and flowering of R. gigentea plants. Some latest media tried for growing orchids are gravel jelly, fir bark, tree fern fibre and polyurethene foam.

In nature, orchids obtain their supply of inorganic nutrients like calcium, magnesium, iron, potassium, nitrogen and traces of manganese, boron, copper, zinc etc. from the tree on which they are growing and also from atmosphere and decaying vegetables and dropping of birds. However under controlled conditions they have to be supplied with all these major and minor nutrients. Taking into consideration the special need of different orchids, a large number of fertilizer mixtures, both solid and liquid, are available in market. Liquid fertilizers are much more quickly absorbed and can be applied more frequently. As the orchids are slow growing, slow release fertilizers like osmocote can be used to get very good result. Usage of fertilizers should also depend on stage of growth. During vegetative growth, large quantities of nitrogen are required while during flowering, nitrogen should be reduced and amount of phosphate increased.

We have been getting excellent results by using slow release fertilizer mixtures ( NPK 20:20:20 ) with trace elements and coconut water (20-25 %) applied every week for three successive weeks followed by a 10:20:30 (NPK).

Like all other plants orchids are also pone to a number of diseases caused by fungi, virus, bacteria, insects and pests. The most common diseases in each group are :

• FUNGAL AND BACTERIAL DISEASES
• Leaf spot - caused by Colletotrichum and Gleosporium
• Leaf blight - caused by Pythium
• Collar blocth - caused by Penicilium thomii
• Collar rot - caused by Sclerotium
• Orchid wilt - caused by Sclerotium rolfsli
• Various fungicides like Captan, Dithane, Agrosan and Ceresan are very effective against these diseases

Orchids like other Horticultural crops, may be propagated either sexually or Asexually. Since most of the commercial orchids are highly heterozygous they are not raised through seed and are propagated through vegetative means to get true-to-type plants. Conventional methods like cuttings, division of shoots or Keikis, are followed along with mericloning through tissue-culture techniques.

The propagation of orchids through cuttings is getting popular again and some of the nursery men like to propagate their orchids through cuttings to get uniform plants. The percentage of variation through this method is almost nill as compared to in vitro propagation through tissue culture. Further some orchids like Anaectochilus respond more to vegetative propagation through cutting than any other method.

Most of the sympodial orchids, like Coelogyne, Cattleya, Dendrobium and Cymbidium, are propogated through this method. The method involved consists of dividing large clumps into smaller units. However care should be taken not to divide the plants unless there are 8-10 pseudo-bulbs. Dendrobiums which are very fast growing can be divide every year.

The orchid flowers are irregular, extremely variable in size and shape with sparkling texture. They may be solitary or in spikes emitting the fragrance of lemons, cloves or fresh lavender oil. A few are, however, highly malodorous.

The flower has its parts in threes, i.e. 3 sepals and 3 petals collectively called as tepals due to their resemblance in texture and colour, similar to each other and subsimilar to sepals. It is , however, the third petal which is different and distinctive and is called labellum or the lip. The lip is which is highly polymorphous is responsible for the different names of the orchids like `Frog orchid', `Dove orchid', `Spider orchid', `Lady slipper orchid' etc. The reproductive organs of the orchids, the stamens and pistil, are condensed and form a consolidated complex body, the column the male and female part being separated by a flap or projection of a tissue called rostellum.

Orchid are cross pollinated by insects and birds and to achieve this they have adopted many contrivances like mimicry and twisting of flower on its stalk to almost 180o to face its pollinating agent. A fine example of mimicry is shown by a Mediterranean orchid Ophyrus. It resembles a female wasp and emits the similar odour to attack male wasp. In this attempt to mate with the plant, the male wasp picks up the pollinia and eventually deposits it on the other flower.

A large number of natural hybrid both intergeneric and interspecific have been reported in different genera like Odontoglossum, Phalaenopsis, Cattleya, Laelia, Miltonia and Oncidium. Cattleya guatemalensis collected from Guatemala in 1861 by Skinner was found to be a natural hybrid between Epidendrum aurantiacum and Cattleya skinneri. It was later named as Epicattleya. Similarly, Phalaenopsis intermedia is a natural hybrid between P. aphrodite and P. rosea.

Since 1856 when the first orchid hybrid Calanthe dominyi flowered, a very large number of artificial hybrid have been produced both at intergeneric and interspecific level. To date, more than 125,000 hybrids have been registered with an average of 10,000 or more every year. The success and ease with which such a large number of hybrid are produced every year depends upon the fact that most of the orchids genera and species have no generic barriers and they cross freely with each other. It must be mentioned that most of the orchid genera are still in the process of evolution and most of the orchids groups are in reality only artificial constructs. The other two factor which have played a major role in the development of orchid hybrids are polyploidy and introgressive hybridization. In some genera like Cymbidium, Paphiopedilum, Phalaenopsis, Cattleya, Laelia, Sophronitis, Polyploidy has been of extraordinary effect, and coupled with intergeneric compatibility has culminated in formation of hybrid groups which show both greater size and hybrid vigour as compared to parental species.

• Ascocenda (Ascocentrum x Vanda)
• Aranda (Arachnis x Vanda)
• Aeridovanda (Aerides x Vanda)
• Brassocattleya (Brassovola x Cattleya)
• Vandanopsis ( Phalaenopsis x Vanda)
• Laeliocattleya ( Cattleya x Laelia)
• Sophrocattleya ( Cattleya x Sophronitis)

• Arachnis - ` Maggie Oei'.
• Aranthera - `James Storie'
• Aeridochnis - `Bogor'
• Aranda - `Christine'
• Dendrobium - `Pompadour
• Dendrobium - `Walter Oume'
• Dendrobium - `Tomie'
• Dendrobium - `Spell Bound
• Dendrobium - `Ceasar
• Vanda - `Miss Joaquim
• Vanda - `Rothschildiana
• Asconcenda - `Yip Sum Wah
• Oncidium - ` Golden Shower

The most interesting and Adaptive feature of the family Orchidaceae is the physiology of its seed germination Orchid seeds are unique in several respects. They are exceedingly small and dust like and are produced in very large numbers. As many as 1,300 to 4,00,000 seeds per capsules are produced. Their colour may be white, cream, pale green, reddish orange or dark brown and have very diverse shapes.
Orchid embryo consists of relatively undifferentiated, most isodiametric cell with dense granulated cytoplasm and lose their viability very fast.

Most of the Mycorrkihzal fungi of orchids fall into a non-sporing group known as Rhizoctonia, the major species being R. repens, R. mucoroides and R. languinosa. Subsequent isolates were known as Mycelium radicis. For quite some time these fungi were called as Orcheomyces. Later on, however, other fungi were also isolated from orchid cultures. In Japan 54 different fungi were isolated from 20 orchid species.

Orchid seeds cannot utilize their own reserve or do so very slowly, they can also not hydrolyse large molecules like starch or cellulose. As a result asymbiotic germination in the absence of sugar proceeds only to the early protocorn stage, after which they wait for external supply of simple sugars through the help of Mycorrhizal fungus.
Until the middle of 19th century European growers had no method for germination of orchid seeds, and no hybrid could be produced, the only method followed was sowing of seeds at the base of the mother plant but in most of the cases the seed either did not germinate, got mixed up or took too long to germinate. This was later followed by Bernards method in which culture tubes were inoculated both with seed and fungi but the method was very elobarate and left much to be desired.

While working on the influence of the corbohydrates on green plants, Lewis Knudson in 1916 also started experimenting with the germination of orchid seeds on the basis of the analysis of orchid salep which contained starch, protein, sugars and minerals, he formulated a medium and successfully germinated seeds of Cattleya, Laelia, Epidendrum and concluded that fungus was not necessary for orchid seed germination.
This was the breakthrough in orchid seed germination and was followed by other who tried to improve the original media of Knudson in order to germinate other orchid species. When the seeds are planted on a nutrient medium in vitro not only the percentage of germination is improved in some cases to 100% but it also takes less time for further development. It may be mentioned here that an orchid seed while growing differentiates both bio-chemically and morphologically.

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