Germination Monitoring
Seeds germinating on Agar
A germination test is the most reliable test of viability. It is also the most useful viability test because conditions are identified that can be used in the future to turn the seeds into plants for reintroduction, restoration or research. However, most of the species in the Millennium Seed Bank will never have been germinated in a laboratory before. The conditions needed for germination are known to vary considerably between different species and even between different populations of the same species. MSBP scientists use knowledge about the plant such as its ecology and life cycle as well as climate information to predict the optimum conditions for germination and the form of any pre-treatment that may be required to overcome seed dormancy.
The viability of MSB seed-lots is assessed about one month after they are placed into the -20°C cold store. Testing them at that time checks that seeds of a given species are able to withstand the banking process. Germination is subsequently re-tested at approximately 10-year intervals. The basic test procedure is very simple:
Cold room: jars containing seeds of Afzelia africana
1) A seed container is removed from the cold room and allowed to warm up for one day in the adjacent drying room. A suitable quantity of seeds is then removed. The quantity is the product of the number of dormancy-breaking treatments at a given stage of testing and the treatment sample size. The number of seeds in each treatment sample is usually 20 seeds. For very small collections, as few as 10 seeds may be used, although seed-lots with less than 500 seeds are usually left untested. Very small germination tests do not yield data capable of statistical analysis but do give an indication of success of dormancy-breaking treatments and general level of viability.
2) The seeds are sown onto 10 g l-1 water agar.
Illuminated incubator
3) The test is placed at an appropriate temperature in an illuminated incubator (8 h fluorescent light / 16 h dark).
4) Germination is recorded (usually a 1 - 2 mm protrusion of radicle) at weekly intervals and the germinated seeds removed and discarded. Although radicle emergence is a relatively lax measure of germination, it appears possible to relate it to other measures such as radicle plus shoot growth and viability as determined by vital staining.
Seeds germinating on an agar plate
Tests are usually examined in a clean air cabinet, to minimise the risks of inhalation of fungal spores produced by any mould growing on the seed.
5) When germination is judged to have stopped, the test is terminated and the remaining seeds evaluated by visual inspection and a cut-test to ascertain whether they are full, empty or mouldy. Excessively mouldy, yet filled, seeds indicate loss in viability, particularly if very soft. For wild species it is not unusual for each test to take many weeks or even months. The germination pass level for the MSB collections is 75 % (after empty and damaged seeds are taken into account). Failures may be regenerated, discarded or kept, dependent upon the rarity of the material, the level of germination and the potential ease of regeneration. Re-collection may be considered for some material if possible.
Collections are also monitored for moisture status.
