Complex sentence: Seed is only provided from appropriate collections in the MSBP when the collection is sufficiently large and the UKNSH has the authority to provide it, where this is not possible species may be bulked up on the production beds.
Split into simpler sentences: Seed is only provided from appropriate collections in the MSBP when the collection is sufficiently large. Where there is not sufficient seed numbers to make a collection available for distribution the species may be bulked up on the production beds.