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

Seed survival of cryostorage (-196 degrees C) was examined for Banksia ashb yi (E.G. Baker), a tree species endemic to Western Australia. Seeds were cr yostored 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 affe ct seed germination or vigour (radicle growth). Seed age influenced surviva l with freshly harvested seeds showing a greater tolerance to cryostorage a t high moisture contents than older seeds. Exotherms, indicating ice format ion 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 plasm a membrane of cells remained intact. This study shows that seed storage phy siology of a Western Australian species is similar to that of other orthodo x species and that cryostorage may be successfully applied for conservation of native species without detrimental effects on germination and growth.