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Orchid Propagation Techniques

Prepared by:

Dr. Sheena McKendrick, CFTC Intern, March 2000 

Introduction 

A research program testing a variety of techniques for raising orchid seedlings was conducted from February 2000 to mid-2001.  The original purposes of the program were to find methods using inexpensive materials to successfully rear orchids from seeds.  Such techniques could be used to propagate orchids from wild stock, and then reintroduce them to native habitat, or to produce orchids for sale and funnel the proceeds back to reserves from which the original seed stock had come.  Due to lack of funding, neither long-term goal was met; however, we learned a great deal about orchid propagation that may be of use to others with similar interests.

Techniques employed 

In vitro germination of orchid seeds 

Orchid seeds are not like other seeds in that they are tiny (they are often referred to as dust seeds) and contain few food reserves. In nature they usually will not germinate unless infected by a particular fungus, which feeds the young plants with all the sugars and nutrients they need until the plants are large enough to produce their own food. Once the seed has germinated it produces a fairly undifferentiated mass of cells called a protocorm (see picture). All being well this protocorm will continue to grow for many weeks, months or even years depending on species, until large enough to produce leaves and roots. In terrestrial orchids it is vitally important that the orchid/fungus relationship is maintained as the protocorm is underground or under leaf litter and cannot produce any food of its own. In epiphytic orchids the protocorms are often green, and thus can produce some food of their own. Epiphytic orchids are still thought to be dependent on the fungus for the germination, but little research has been done in this area and so nobody knows for sure.  

In in vitro germination the seeds are germinated under sterile conditions in glass dishes or jars on a gel-based medium which contains all the sugars and minerals the seeds need to germinate and grow. The media, to a certain extent, mimic the nutrients which would have been provided by the fungus and allow the seeds to germinate and grow without it. The media and the jars used are first sterilized by subjecting them to high temperature and pressure for 15 minutes in an autoclave, then the media allowed to cool and set. Sterile conditions for pouring the media and sowing the seeds are obtained using a laminar air-flow bench. This bench is enclosed on all three sides and the top. Air is sucked in from the back of the bench and blown through filters over the bench. The filters filter out any bacteria and fungi in the air and the air flow normally prevents any spores in the air just outside the bench from floating in. Thus, if the bench is thoroughly sterilized with alcohol before work commences, and care is taken not to introduce contamination, it should remain sterile. Sterility is important as any bacteria or fungi introduced to the flasks will grow much quicker than the seedlings and may over/run and kill them.

Two methods employed for germinating the seeds

1.  Sowing from green capsules (left). The inside of orchid capsules, if intact, are naturally sterile. Therefore if you sterilize the outside of the capsule, where bacteria and fungi can collect, and cut open the capsule under sterile conditions then the seeds should be sterile. This method has the advantage that the seeds themselves do not need to be sterilized (which can sometimes lead to damage). In addition, some seeds, if taken from capsules which are almost ripe, germinate quicker than those taken from mature capsules as the dormancy mechanisms are not yet in place. It has the disadvantage that once opened all the seeds from a capsule must be sown or discarded.

2.  Sowing from mature seeds. Once a seed capsule has opened naturally, the seeds are no longer sterile. The seeds thus need to be sterilized, usually using a solution of sodium hypochlorite (bleach), calcium hypochlorite or hydrogen peroxide. The seeds are shaken in a solution of sterilant containing a drop of detergent to wet the seeds, then rinsed in sterile water and planted on to the medium. This method has the advantage that seeds can be collected, air-dried, stored for many months in the fridge and used when needed. Germination from mature seeds has already been achieved successfully with Trichopilia fragrans.

The in vitro propagation program tests were carried out at the Universidad San Francisco de Quito (USFQ), where we were provided access an autoclave, laminar air-flow cabinet and growing facilities necessary to germinate and grow the orchids under sterile conditions.  Ceiba would like to thank Dr. Nelson Zaballa and Dr. Stella de la Torre of USFQ for their generosity, and Monica de Navarro for her invaluable expertise and support.  Without their tireless assistance, this research would not have been possible.

Conclusions

Seed germination can bea very important tool in the conservation of wild orchids through the propagation and distribution of rare and endangered orchids, and potentially through the propagation and sale of unusual and ornamental species in order to provide funds for the on-going protection of habitat reserves.

Orchid Propagation Manual 

To download a copy of CFTC's Orchid Propagation Manual select from the following formats: 

English - MS Word (.doc - 62k)  •  English - Adobe Acrobat (.pdf - 46k) 

Spanish - MS Word (.doc - 89k)  •   Spanish - Adobe Acrobat (.pdf - 49k) 

If you are unable to view the Propagation Manual, please contact CFTC to receive a copy.