Tropical Orchids of Southeast Asia. David P. Banks

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      Orchids have always held a fascination for people; there is an air of mystery surrounding them. Mention the word "orchid" and terms such as exotic, rare, expensive, beautiful, colourful and unique will arise. Everyone will have a different perception and all of these, no matter how diverse, will be correct.

      Over 30,000 different orchid species are found on our planet, and well over 100,000 hybrid strains have been artificially propagated. Many of these hybrids are important commercial plants that are used as cut flowers and pot plants to satisfy strong demand, both locally and internationally.

      What makes orchids different from other flowering plants? Their floral structure is obviously different. Orchids have three petals and three sepals which may, or may not, be alike. However, the third petal, known as the lip or labellum, is almost always highly modified and quite different from the other segments in size, shape and often colour. This structure often plays an important part in orchid pollination. Another feature, which helps to define orchids, is an appendage, known as a column, often located in the centre of the flower. The fleshy column combines the male (anther) and female (stigma) sexual parts on one structure. The anther and stigma are situated close together.

      Orchid flowers use their form, colour and often fragrance to attract many creatures which act as pollinators. Bees, wasps, butterflies, moths, flies, beetles, ants and even birds assist the fertilisation of orchid flowers. Numerous orchid flowers actually mimic insects. Some deceive bees by looking like other flowers that offer a reward, while other species, often with deep maroon flowers, smell like rotten flesh, to attract flies!

      Two main growth structures are found in orchids; monopodial and sympodial. Sympodial orchids, such as Bulbophyllum and Dendrobium, have a main stem, or pseudobulb, which is produced annually and matures at the end of each growing season, often culminating with flowering. During the next season, a new pseudobulb grows from the base of last season's growth. These pseudobulbs, which hold water and nutrients, are produced along a structure known as a rhizome. Monopodial orchids such as Aerides, Phalaenopsis and Vanda have main stems which grow constantly. These main stems produce flower spikes, correctly termed inflorescences, from or opposite the leaf axil.

      Orchid seeds are minute and dust-like—a single fruit or capsule has the potential to produce up to a million seeds, depending on the species. However, orchid seeds have little food storage and rely on a specific type of fungus for their germination and development. The mortality rate in the wild is enormous. Now, orchid seeds are germinated in laboratories СКАЧАТЬ