Читать книгу Tropical Orchids of Southeast Asia - David P. Banks - Страница 6

Introduction

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 using a synthetic agar solution. This technique has made it possible to produce large quantities of both species and hybrids in a sterile environment. Depending on the genus, orchids can take from twelve months to twelve years from germination to flowering. On average, most orchids flower around four years from germination after starting out in life as green blobs known as protocorms.

Amesiella monticola

Ascocentrum pumilum

One fact that quickly becomes apparent is that few orchids have "common" names. Many are simply referred to by their generic name. Many other groups of plants are known by their botanical names, as common names, often without the users knowing it. Such tongue-twisting examples include Agapanthus, Bougainvillea, Chrysanthemum, Jacaranda and Rhododendron. These names are derived from both Latin and Greek, however, Latin has been used extensively for scientific terms. This enables a universal system for communication. A problem with common names is that one name may refer to many completely different plants. Also, what may be a "local" name in one area may not be pertinent in another.

Over 75 per cent of the world's known orchid species occur in the tropics. This is a fact that doesn't surprise many. What may surprise, however, is that the majority of these "tropical" species (over 80 per cent) inhabit the cooler mountainous forests, at altitudes of over 1000 metres above sea level. These montane forests provide homes for an amazing number of diverse and unique plant and animal species. Isolated high peaks, such as Mt. Kinabalu in Sabah, have a high percentage of endemic species that are found nowhere else in the world.

In the tropics, most orchids are epiphytes, that is, they grow on trees for support and light. They are not parasitic, as they do not take food from the tree. Some species grow exclusively on rocks, and are known as lithophytes. Species that grow in the ground are referred to as terrestrials. Most of the tropical terrestrial orchid species are evergreen, unlike the deciduous terrestrials, which are generally found in more temperate climates. After flowering, these plants die down to storage organs, known as tuberoids, which have a similar life-cycle to bulbs.

Dendrobium devonianum

Paphiopedilum druryi

A small percentage of orchids are saprophytes; these live off dead or decaying matter. There are even two Australian orchid species which grow and flower completely underground!

Only a small percentage of the world's orchid flora is cultivated in specialist nurseries, botanical institutions and private collections. Whilst the collection of popular species from the rainforests can threaten the survival of wild orchid populations, their main enemy is habitat destruction. Southeast Asia is one of the world's most densely populated regions, and its virgin forest continues to be cleared and burnt. New species continue to be discovered, and a number of "lost" species have been relocated. Yet one wonders how many species, both plant and animal, have become extinct before they have even been recorded.

Fortunately, most of the horticulturally attractive orchid species are entrenched in cultivation and have been propagated by division or by seed. The species at real risk are the countless miniatures, or "botanicals", as they are known. These have little commercial value and are of most interest to botanists and orchid species enthusiasts.

Hopefully, this book will dispel the myth that most orchid species look the same. In fact, these wonderful plants come in a huge array of shapes, sizes and colours, and are highly specialised. The tropical orchid species shown of the following pages represent the tip of an enormous iceberg.

Orchids will continue to captivate future generations with their unique beauty—indeed they are the monarchs of the plant kingdom.

—David P. Banks