To improve orchid seed longevity, we tested a technique that enables the simultaneous storage of orchid seeds and the fungus required for germination.
The technique, known as encapsulation-dehydration, consists of mixing the seeds and fungus together in a solution of sodium alginate, then pipetting the mixture drop-by-drop into a solution of calcium chloride to form individual beads. The beads are soaked in a sucrose solution and are then dehydrated prior to storage.
We conducted an experiment to determine the effect of storage temperature and storage duration on the ability of the fungus to grow, and the seeds to germinate, when stored in this way. To date, we have successfully germinated seeds of several Pterostylis and Diuris species held for up to two years at -196°C. The seedlings produced during the experiment were very robust and were able to be transferred directly from the laboratory to pot culture, a procedure that often incurs heavy losses in orchid propagation.
Encapsulated orchid seed and fungi are sown on oatmeal agar to encourage fungal growth (A) and seed germination (B).