Orchids show different growth forms such as terrestrial, epiphytic and some are lithophytic. About 70% of orchids in the world are epiphytes. Most temperate orchids are terrestrial while tropical orchids are epiphytic or lithophytic. Epiphytic orchids grow and attach to host trees or to small twigs at the top of the tree's canopy. Epiphytes usually have a strong, developed root system and expose them to the air or crack and bark of the host tree to absorb moisture and nutrients. Terrestrial orchids grow in humus or leaf litter on the forest floor and can adapt to various growing conditions such as swampy ravines, moist forest floors, sand dunes, and even semi-arid desert terrain. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Terrestrial orchids form tubers in the soil and use their underground roots to obtain soil nutrients. Terrestrial orchids have deciduous flowers and leaves as they fall during the winter. Lithophyte orchids grow on the exposed rocks. The leaves of the lithophyte orchid usually looked fleshy. The roots will reach into the cracks to receive water and nutrients from rainwater, surrounding moss and organic debris. Lithophyte orchids have pseudobulbs that can store water to help the plant survive during periods of drought. Growth Cycle and Growth Pattern of the Orchid An alternating cycle of growing periods and resting periods controls the life of the orchid. By exposing themselves to too much humidity during the dormant period, orchids will not flower and will only form weak shoots. The growth pattern of orchids can be divided into monopodial and sympodial. Monopodial orchids grow from a single central stem with leaves on both sides while sympodial orchids exhibit multiple growths and usually develop one or more new growths per year. Each new growth comes from the side of the one and in a circular pattern. Dendrobium (subfamily: ‎Epidendroideae) is one of the most popular genera of the Orchidaceae, with approximately 1,523 species worldwide. Dendrobium belongs to the sympodial epiphytic orchid, it was recognized by Olof Swartz in 1799. Dendrobiums are distributed in tropical regions where there is high annual rainfall and without too much seasonal variation throughout the year. Dendrobiums are native to Southeast Asia and are found in habitats diverse except in the coldest and driest regions. The life cycle of the Dendrobium orchid includes the flowering phase, the growth phase and dormancy. They grow rapidly from summer to fall and remain dormant through the winter. New shoots will form and begin to flower in spring. Dendrobiums can be divided into evergreen and deciduous. Evergreen Dendrobiums flower on new growth, have cane-like stems and papery green leaves, bear flowers in erect panicles and singly at nodes. Deciduous dendrobiums flower on old canes, dry up and shrivel like bamboo canes after the leaves fall. Dendrobiums do not utilize the host's food supply as they have a specialized root structure to absorb water and accommodate mycorrhizal fungi for nutrients. Some stems (pseudobulbs) are green and succulent while others are long, thin, swollen and fibrous. Dendrobium flowers are small to medium in size with a narrow claw lip or no side lobes. Some Dendrobiums can self-pollinate and others are pollinated by insects. Dendrobiums will produce fruit capsules and very small seeds with aspherical ovoid embryo inside each seed. Dendrobium needs a lot of light to grow well and approximately 75% of sunlight is required for plant growth. Dendrobium can tolerate direct sun in the early morning or evening, but requires shade between 11am and 3pm where the light intensity is too high. Optimal light will produce healthy, attractive blooms, while lack of light causes dark green leaves to form. Yellowish or brownish leaves with spots on the underside represent sunburn. Dendrobium grows best at night temperatures between 15-18ºC and day temperatures between 23-29ºC. About 50-75% humidity is required for Dendrobium and excessive humidity will cause fungal and bacterial infections. Infection can be reduced by circulating air to cool the plant. Aeration is important to maintain the health of the orchid and dry out excess moisture. Dendrobiums prefer rainwater and are watered once a week. The roots are very sensitive and easy to rot. Therefore, Dendrobiums are always watered again after the soil has dried. Commercial Value and Market Demand of Orchids Cultivation of orchids began in 500 BC and is used for ornamental and medical purposes. The flowers they produce are extremely exotic and attractive, curious shapes, different colors, longer own life, making them one of the top ten "cut flowers" in the international flower market. Orchids are commonly used as cut flowers and potted plants. They have huge demands and high prices in the global floriculture market due to several properties. Cattleya Labiata is the most popular orchid species and is known as the "Queen of Orchids" due to its colorful appearance and wonderful aroma. Cattleya is widely used in brooch accessories and floral decorations. Due to the small size of the flowers, the Cymbidium orchid is also used as a brooch accessory. Their tall stems, long leaves and long-lasting aroma make them a top choice for orchid lovers. Dendrobium with a wide variety of colors and shapes has a high demand in the international floriculture market. Miltonia orchids have large flowers making them ideal for bouquets and perfumes, as well as indoor flowers. Phalaenopsis is known as the “Moth Orchid” because the flowers resemble a flying moth. For most beginners, these plants are the orchids of choice because they can tolerate many conditions. Vandas is known as the "Singapore Orchid" and comes mainly from Southeast Asia. Their flowers bloom in different colors and their stems are long. Vandas can be placed in the hanging basket. Orchids have been widely used in traditional Chinese medicine. Many orchids have been proven to have medicinal properties. Medicinal orchids mainly belong to the genera: Calanthe, Coelogyne, Cymbidium, Cypipedium, Dendrobium, Epthemerantha, Eria, Galeola, Gastrodia, Gymnadenia, Habenaria, Ludisia, Luisia, Nevilia and Thunia. Orchids contain phytochemicals such as alkaloids, flavonoids, carotenoids, anthocyanins, sterols, bibenzyl derivatives and phenanthrenes. These phytochemicals are important secondary metabolites that can provide antimicrobial, antitumor, anti-inflammatory, antiviral, and other functions. Nearly 145 bioactive molecules have been isolated from various species of orchids, which are used to treat several ailments such as tuberculosis, stomach disorders, jaundice, eczema, inflammation, menstrual disorders, diarrhea, muscle pain, rheumatism, malaria, wounds and sores . Several species of orchids are used as potent inhibitors against gram positive and gram negative bacteria.