Processing - cleaning and testing the seeds
1. Assessment of likely seed storage characteristics
2. Seed cleaning
3. Visual check on the quality of the collection
4. Seed quantity determination
Weighing small seeds on a seven decimal place balance
Several methods are used to estimate the number of seeds within accessions. The determination is recorded on the Seed Bank Database (SBD) which calculates the final seed quantity. If fruits are to be stored and therefore counted, then the number of seeds per fruit must be recorded. The method used to estimate quantity depends on a number of factors:
1) For most collections, a 4 or a 7 decimal place balance (dependent upon seed size) is used to weigh five samples of 50 seeds or fruits. The remainder of the collection is then weighed. The upper 95% confidence limits for the weight of a 50 seed or fruit sample is calculated, which provides a general underestimate of quantity when divided into the total collection weight multiplied by fifty. Underestimating the seed quantity ensures that the collection will not be exhausted earlier than expected.
2) If seeds are exceptionally small (e.g. those of Orchidaceae and Orobanchaceae), a sample of 250 seeds is weighed, then the entire collection and an estimate of the quantity made accordingly.
3) If there are only a few seeds/fruits (<300), they are counted individually.
4) A collection may be counted entirely by a seed counting machine, if it is clean and has suitably sized seeds/fruits. This method is too slow for very large collections.
5) X-ray analysis is sometimes required to determine to proportion of empty or infected seeds.
5. Drying
6. Packaging
