Initiated in 2007, the OSSSU project (osssu.org) was designed to promote seed collecting, storage and research in Latin America and Asia. 25 countries all over the world are now taking part in the project, but despite the existence of a good network of orchid enthusiasts and historic collections, nothing had been done in the UK to this date.
Two two-day workshops, sponsored by the Stanley Smith Horticultural Trust were organized last month, gathering National Collection Holders, commercial growers and horticturalists from around the country. Having done my master’s thesis on orchids, I was thrilled to be invited!
The first workshop was held at King Charles 1st School in Kidderminster. Phil Seaton, our orchid expert, has been working with students since 2005, studying and growing both local and tropical orchids, and even has his own lab at the school. The second workshop took place one week later at the Millenium Seed Bank in Wakehurst Place, where Tim Marks, our seed expert, is studying the biology of seed storage.
Plants had kindly been brought by some of the participants, which led to interesting conversations (“Will this Cymbidium blush by tomorrow?” – orchids flowers can change colour after pollination…sadly, this one didn’t).
Some orchids like Pleurothallids are cleistogamous, which means that the flowers stay closed and pollinate themselves. Most orchids however are pollinated by insects, and replacing bees or flies with a human hand is not always an easy task! Armed with a toothpick, we first practiced on the large flowers of a common Phalaenopsis, but the pros soon moved on to more challenging blooms. Here, Gary Firth, National Collection Holder, and Mariano Medda from the Eric Young Orchid Foundation are sharing expertise on the pollination of Gongora.
Once the seeds are ripe, small packets will be used for storage. It was time for a little origami session in the lab, testing all sorts of folding methods and materials. Scientists tend to use small discs of expensive filter paper, but coffee filters do the job very well.
Orchid seeds are among the smallest in the plant world (hence their nickname of “dust seeds”), so special care is needed while handling them. This little flask probably holds a few millions of Cymbidium seeds!
Seeds can be put in a Petri dish on wet paper to rehydrate them, and observed under a microscope. Orchid seeds come in all sorts of sizes and shapes : note the difference between the black, opaque, rounded seeds of Vanilla and the long, thin seeds of the Common Spotted-orchid, Dactylorhiza fuchsii.
Before sowing seeds, it is possible to assess their quality with a quick and relatively simple test. The chemical tri-phenyl tetrazolium chloride (let’s call it tetrazolium!) changes from colorless to red when put in the presence of cells which are respiring. On the first day of the workshops, we all carefully placed seeds in test tubes containing a tetrazolium solution. They were left overnight in the dark and viewed under a microscope the next day. This is the result : the rounded embryo of these Cymbidium seeds is stained in red, which is good news – they are alive and very likely to germinate. The surrounding tissue, or “testa” is not stained because it is made of dead cells filled with air (useful for wind dispersal).
Once the seeds have been deemed viable, it is time to sow them. Well-equiped labs will use all sorts of growth media with exciting names such as MS/2, KC and ½B5C, but orchid seeds can also germinate on a simple medium made of water, agar and oats (yes, the same oats you’re having for breakfast).
The seed packets are sterilised in bleach (no publicity intended!), rinsed in water, opened by cutting the top and dabbed over the surface of the medium to lay the seeds. Finally, the Petri dishes are sealed and placed in the dark….and that’s it!
We all went home with Petri dishes containing seeds of Dactylorhiza and Aerides. If we’ve done our work correctly and avoided contamination, the seeds should start germinating soon and develop hairy roots. They can then be moved to larger flasks as the seedlings grow. These Common Spotted-orchid plants were sowed in May 2012, and are now ready to be transplanted in soil.
The outcome of the two workshops has been very positive.
The participants went home with documentation (including the informative book “Growing Orchids from Seed” written by Phil Seaton), technical sheets, silica-gel and flasks to store seeds. Many are willing to pollinate their plants (or at least try to!), collect and store seeds themselves in their freezers, or donate them to the Millenium Seed Bank.
Many of the large orchid collections that were popular in the 19th century have now disappeared, yet “ex situ” collections (out of the natural habitat) play an essential role in conservation. We hope to involve as many people as possible in this project, and help safeguard the future of orchid diversity on a global level.