Under natural conditions orchid seeds are released as their capsules ripen and are then carried by winds or air currents until they land eventually perhaps miles away from the parent plant.

They may settle on open soil, in water or on the surface of vegetation but wherever they land the microscopic seeds have only the slenderest chance of survival. The seeds of many if not most species can only develop into seedling plants if they are first infected by a particular strain of a particular species of fungus Rhizoctonia spp) and if they can then achieve a co- existence with the invader by which each benefits from food products produced by the other. This process of mutual benefit is called symbiosis and results from a situation in which strands of fungal hyphae extending from the developing orchid seedling produce excretions which break down complex organic molecules in the surrounding litter into simpler nutrients such as carbohydrates and amino acids. These are transported into the parts of the fungus within the orchid seedling and eventually into the orchid itself. Successful symbiosis depends on the most delicate balance between host and invader. If the latter is too vigorous the host succumbs to the infection; if the resistance of the former is too successful the fungus may never establish itself sufficiently to play its part.

Orchid seedlings can be grown under cultivation by following this natural system; either by sowing seeds close to the roots of established plants, or by sowing seeds on nutrient cultures to which Rhizoctonia spore suspensions are added. However, it is also possible to raise orchid seedlings entirely artificially without recourse to the fungal partnership by supplying them with all the mineral salts and sugars they need in order to grow healthily.

Raising orchid seedlings in this way avoids the need to establish the delicate balance required for survival of both host and pathogen described in the previous paragraph and is, with many species of orchids, a comparatively simple exercise provided the right techniques are used.

At Kew Gardens the Living Orchid Collection is augmented every year by seedlings raised in the Micropropagation Laboratory. The seeds from which the plants are grown come from a variety of sources, including from plants grown at Kew which are pollinated by hand as required. Many species which are rare or approaching extinction in the wild are increased in this way, as are particularly decorative plants for use in displays. Seeds are also obtained from plants used in breeding experiments, both species and new crosses. They are also used simply to increase the number of plants of species which are hard to grow or represented by only one specimen in the collection.

Kew also receives donations of seeds from many sources. Botanists on expeditions are encouraged to collect seeds rather than plants, thus causing less damage to wild populations. Private growers who have rare plants in their collections are often prepared to provide seeds from plants which cannot be divided, while commercial orchid growers sometimes share a crop of seeds. Other botanic gardens in many parts of the world, and organisations like the Australian Orchid Foundation, also exchange seed with Kew. From all these sources, new species are added to the orchid collection every year as young seedlings, the stage at which they are most adaptable to glasshouse culture.  Sending seeds rather than plants around the world has many advantages. They are extremely light and several thousands can be packed in a small envelope. CITES controls apply to seeds of orchids listed in Appendix 1, while European Community Regulations affect the movement of seeds of most European orchid species. When they are received, seeds can be stored in a domestic refrigerator for short periods but should be sown as soon as possible.


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The Micropropagation Unit

It is now some 30 years since Peter Thompson started working in the Jodrell Laboratory on a new formulation for a medium for the germination of orchid seeds. In the course of this work he succeeded in germinating seeds and raising seedlings of a wide range of genera. His book Orchids from Seed is still widely used as an introductory guide to micropropagation. In 1974 a Micropropagation Unit was set up at Kew to make in vitro propagation techniques available to the gardens for a wide range of plants including orchids.

The Micropropagation Unit occupies the whole of the ground floor of Aiton House, situated in the Lower Nursery area of the Gardens. The main laboratory has offices, preparation, autoclave and store rooms adjacent to it. There are separate rooms where the laminar flow cabinets are kept at which all sterile techniques are carried out. Next to these are the air-conditioned growth rooms with racks of illuminated shelves where the young plants are grown in vitro. Growth cabinets where light and temperatures can be carefully regulated for small batches of flasks are also available. The unit has its own range of glasshouses where all the transfers of young plants to compost are made and the seedlings can be weaned under very humid conditions.


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Seed Collection and Storage

Seeds of most orchids take a long time to mature and it is not unusual for many months or even a year to pass, after pollination of the flower, before the capsule is ready. As the green capsules ripen they often change colour, becoming yellow or brownish. Narrow slits appear along the sides, or along the ventral surface during the ripening process, and the seeds are usually released gradually over a period which can range from several days to weeks or months. It is therefore important to watch capsules ripening in the glasshouse and harvest them before they split. Each capsule is cut off and stored separately in a small labeled jar until all the seeds can be tapped out in the laboratory. In all cases capsules which have not yet dehisced are preferred and the technique for using them is described later in this chapter.

Orchid seeds are very small. Unlike the nutrient solutions, they cannot be sterilised by heating, because this would kill them, so a chemical method is usually used instead. Sodium hypochlorite, the active ingredient of most domestic bleach, makes a good sterilant. Alternatively, water can be added to fresh calcium hypochlorite which is then filtered after five minutes. A strong solution containing chlorine is thus obtained, which must be used with care.

Various culture vessels have been tried at Kew, including test tubes, Petri dishes, conical flasks, Kilner jars and honey jars. For sowing, pre-sterilised Petri dishes are often used because their flat shape means they can be examined easily under the dissecting microscope. Their disadvantage is that the medium they contain dries out more quickly than in a larger container. When germination has begun, the protocorms are replated to a larger container for further growth. Small honey jars with plastic caps are frequently used at this stage.

Terrestrials and epiphytes are arranged separately on the staging as they need different kinds of management. After watering﷓in, the terrestrials require rather little additional water until they are well established and growing rapidly. The epiphytes are also watered-in and then misted-over thoroughly several times each day for the first few weeks after deflasking. This is necessary to prevent desiccation for the leaf cuticle of the seedlings is poorly developed while they remain in the flasks. The pots are watered frequently, too, just before the compost dries out. As the seedlings root more strongly, the misting becomes lighter and less frequent, until, by the late autumn, misting once a day in the early morning is sufficient. Seedlings are fed each week with a dilute balanced fertilizer.

Most of the seedlings remain in the seedling house for about a year. However, some epiphytes from high altitudes require a cool, dry winter, and these are moved in the autumn so that they can experience conditions similar to those of their natural habitat at an early stage. All the rest of the orchid seedlings are moved to the main orchid collection at the end of the winter. Then the seedling house soon fills up with the new season's young plants.


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Some Successes

The species Cattleya dowiana is rare in cultivation because it requires more humid conditions than many other cattleyas, and because plants imported from the wild have been difficult to establish. It has become rather rare in the wild because its habitat, along cliff edges in humid forests at medium altitudes, always where there is high humidity and plenty of air movement, has become greatly reduced by development and because plants in accessible places have been collected for sale. On a short visit to Costa Rica in 1986, Joyce Stewart was given a small packet of seeds by Clarence Horich, a resident of Costa Rica who has sent many specimens to Kew.

Cattleya dowiana, a species which is greatly reduced in Costa Rica because of loss of habitata  and over-collection; wild collected plants have always been difficult to grow in cultivation

Epidendrum ilense from Ecuador was known from only six plants in the wild when it was propagated at the Marie Selby Botanic Gardens, Sarasota, Florida, and a small plant given to Kew. The area the species came from was completely deforested and for a few years it was thought to be extinct in the wild. Recently, another small population has been discovered, but even in that area the future of this unusual species is also precarious. Seeds were collected from the Kew plant in 1986 and 1987. They germinated on several different media. The small seedlings were transferred to half strength Murashige and Skoog medium, supplemented with banana pulp or activated charcoal. They grew well on both these media and plants have since been widely distributed.

Epidendrum ilense from Ecuador was known from only six plants in the wild when it was propagated at the Marie Selby Botanic Gardens, Sarasota, Florida, and a small plant given to Kew. The area the species came from was completely deforested and for a few years it was thought to be extinct in the wild. Recently, another small population has been discovered, but even in that area the future of this unusual species is also precarious.

Seeds were collected from the Kew plant in 1986 and 1987. They germinated on several different media. The small seedlings were transferred to half strength Murashige and Skoog medium, supplemented with banana pulp or activated charcoal. They grew well on both these media and plants have since been widely distributed.

Seeds of Clowesia rosea, an endangered and very beautiful orchid, were sent to Kew by Ed Greenwood who lives in Oaxaca and who has been supplying Kew with orchid seeds from Mexico for the last 15 years. This Clowesia grew best on Vacin and Went and on half strength Murashige and Skoog medium when these were supplemented with activated charcoal.

Strong plants are now thriving in the glasshouses at Kew and have been distributed to other gardens and growers. Other successes with Mexican orchids include several attractive species of Encyclia.

The 'lost' species Cymbidium rectum was rediscovered by the botanist Tony Lamb in Sabah. It differs from Cymbidium bicolor in having an upright raceme, an unusual characteristic in this section of the genus. The habitat where a few plants were rediscovered has since been clear-felled and it is likely that the species is extinct in the area now. Seeds were sown in 1983. The resulting seedlings grew most vigorously on Vacin and Went or half strength Murashige and Skoog medium with activated charcoal. Like the other species discussed above, this Cymbidium has now been distributed to many institutions and growers.

Gynoglottis cymbidioides is the only species in this curious genus. It occurs in Sumatra at about 1550 m altitude and it was unknown in cultivation until seed capsules were collected by Jim Comber in 1988.

The species resembles Coelogyne in habit, but has rather small white flowers of distinct structure in a long, many-flowered raceme. The seed capsules were undehisced on arrival at Kew and seeds germinated within two weeks of being sown. Surplus capsules were sent to Richard Warren in Edinburgh who raises a wide range of tropical orchids from seeds for sale.

Seedlings are now growing well in vitro and have been distributed in flasks to other institutions with facilities for growing﷓on plants under in vitro conditions.

These success stories are only a sample of the routine work of orchid propagation carried out by Dickon Bowling in the Micropropagation Unit under the supervision of Dr Michael Fay. Though primarily a service to the living collections at Kew, the work is increasingly involved with conservation, either by the return of propagated plants to their place of origin, or by the distribution of surplus seedlings to growers in other botanic gardens and elsewhere. It is likely that this work will become increasingly important as the wild orchids throughout the world continue to disappear and as national and international legislation controls the movement of wild-collected plants.

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see also Mycorrhiza and Germination

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