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X-ray analysis

X-ray analysis helps us ensure that seeds saved by the MSBP are of the highest quality.
A sample of Terminalia brachystemma fruits. Although the fruits all appear to be healthy, six contain empty seeds

An x-ray gives a clear image of the internal morphology of the seed or fruit. The x-rays are generated using very low voltages (much lower than are used for most medical applications) and the method is safe with the appropriate precautions. However, because there is a very small risk of genetic damage, the sub-sample is either discarded or used for germination testing.

The seed samples to be x-rayed are laid out in Petri dishes or plastic grids with machine-punched holes set in a regular pattern, backed with waxed paper. The Millennium Seed Bank uses a Faxitron digital x-ray machine.


Adesmia balsamica seeds with infestation

Of particular interest are the outwardly normal, but 'empty' seeds that regularly occur in collections of wild species. Allowance must be made for this incompetent fraction of the collection when germination and seed quantity are determined.

Insect larvae living within seeds are sometimes detected by x-ray. The image above shows Adesmia balsamica seeds containing insect larvae.