Moisture content influences survival of cryostored seed of Banksia ashbyi (Proteaceae)

Abstract

Seed survival of cryostorage (–196˚C) was examined for Banksia ashbyi (E.G.Baker), a tree species endemic to Western Australia. Seeds were cryostored over a moisture content range of 3–30%. Moisture contents of 18–20% significantly depressed survival for seed of all ages tested (1 month to 13 years old). Cryostorage at seed moisture contents below 18% did not affect seed germination or vigour (radicle growth). Seed age influenced survival with freshly harvested seeds showing a greater tolerance to cryostorage at high moisture contents than older seeds. Exotherms, indicating ice formation within seed tissues, were detected by thermal analysis at seed moisture contents above the critical. However, there was no increase in electrolyte efflux from seeds frozen at lethal moisture contents, suggesting the plasma membrane of cells remained intact. This study shows that seed storage physiology of a Western Australian species is similar to that of other orthodox species and that cryostorage may be successfully applied for conservation of native species without detrimental effects on germination and growth.