Cymbidium (PROSEA)
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Introduction |
Cymbidium Sw.
- Protologue: Nova Acta Regiae Soc. Sci. Upsal. 6: 70 (1799).
- Family: Orchidaceae
- Chromosome number: x= 20;C. aloifolium: 2n= 40,C. ensifolium: 2n= 40
Origin and geographic distribution
Cymbidium comprises approximately 50 species, and occurs throughout tropical Asia, from India to China, Japan and the whole of Malesia, as well as in Australia.
Uses
There are no reliable records of medicinal applications of Cymbidium in the Malesian region, but whole plants are used in traditional medicine in Vietnam, Thailand, as well as India, China and Australia. Crushed leaves and sometimes roots are used externally to treat arthritis, sores, burns and otitis media. Decoctions of roots and rhizomes are used in China to treat gonorrhoea, syphilis, stomach-ache and problems of the respiratory tract. In Ayurvedic medicine in India, Cymbidium plants are used in mixtures to treat tumours, diarrhoea, vertigo and paralysis. The pseudobulbs are chewed in Australia against diarrhoea and dysentery.
Cymbidium species are of great interest to horticulturists and orchid breeders. Large-flowered plants have been bred for decades, and have been cherished in China and Japan for centuries. Cymbidium hybrids are among the most important commercially grown orchids. They are also commonly grown for cut flowers. The breeding of small-flowered species started on a large scale by the beginning of the 1980s.
Properties
Mannose-specific lectins isolated from a Cymbidium hybrid were highly inhibitory to human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2), and showed additionally marked anti-human cytomegalovirus, respiratory syncytial virus and influenza A virus activity in vitro. They presumably interact at the level of fusion with the target cell. Contact allergy from handling Cymbidium cultivars has been reported, probably due to the presence of the quinone derivative 2,6-dimethoxy-1,4-benzoquinone. Several benzenoids including aloifol, coelonin, 6-methyl-coelonin and gigantol were isolated from the roots of C. aloifolium .
Botany
Terrestrial or epiphytic (sometimes lithophytic) perennial, usually tufted herbs, usually with a short stem, with pseudobulbs at base usually hidden by leaf sheaths, each pseudobulb with a tuft of leaves. Leaves alternate, simple, articulate, duplicative, leathery; stipules absent. Inflorescence a raceme borne at the base of a pseudobulb, erect to pendulous, few- to many-flowered. Flowers bisexual, zygomorphic, often very showy, resupinate, lacking a spur, mostly fragrant; tepals free, subequal, lip (labellum) borne on a short column foot, 3-lobed, usually conspicuously bicarinate at base, median segment recurved; stamen 1, anther proclined, with 2 more or less deeply cleft or furrowed pollinia placed on a common stipe; ovary inferior, 1-celled. Fruit a usually fusiform capsule opening by longitudinal fissures, many-seeded. Seeds minute.
Three subgenera are distinguished within Cymbidium . Subgenus Cymbidium contains many comparatively small-flowered epiphytic or lithophytic species with usually pendulous inflorescences (e.g. C. aloifolium in section Cymbidium ). Subgenus Jensoa contains terrestrial species with upright inflorescences and comparatively small flowers (e.g. C. ensifolium ). Subgenus Cyperorchis comprises the species used in the breeding of large-flowered modern hybrids. Grammatophyllum is apparently closely allied to Cymbidium .
Ecology
Cymbidium can be epiphytic (e.g. C. aloifolium ) or terrestrial (e.g. C. ensifolium ). Epiphytic species are sometimes also found on rocks, whereas terrestrial ones often occur in damp forest in a deep leaf litter. Cymbidium plants prefer some shade, and in cultivation they are best grown in light shade (about 40% sunlight) and high relative humidity.
Management Although Cymbidium can be propagated by divisions, mass in-vitro propagation is often practised for ornamental Cymbidium . Shoot meristems and axillary buds of C. ensifolium and several other species can be cultured on modified Murashige and Skoog medium. The explants form protocorm-like bodies within 4-6 months. When the medium is supplemented with growth hormones buds are formed, and plantlets can be transferred into pots when 3-4 leaves are formed. In general, Cymbidium is fairly easy to cultivate. Black streak virus is a major disease in cultivation. For medicinal purposes, plant parts are often dried after collecting for later use.
Genetic resources
Some institutes have living orchid collections in which many Cymbidium species are represented, e.g. in the Royal Botanic Gardens Kew, United Kingdom. Many smaller-scale Cymbidium collections are maintained by orchid growers. An enormous number of cultivars have been developed ranging from dwarf to robust plants of almost 2 m tall, and to plants with flowers of 10 cm in diameter. Some species may have become rare and endangered because of collecting from the wild for ornamental purposes, which is locally common practice.
Prospects
Cymbidium is highly appreciated for its flowers and sometimes also foliage (the leaves may be variegated), and it will maintain its importance. In addition to to the large-flowered hybrids which have already been grown for decades, smaller-flowered species have also become popular recently. Too little is known about the phytochemistry and pharmacological activities to judge the medicinal prospects, but the few tests that have been carried out showed some interesting antiviral activities.
Literature
69, 831.
Selection of species
Authors
Dzuong Duc Huyen
