Cryopreservation of seed of Western Australian native species

The ability of seed of native Western Australian species to be stored using cryopreservation methods was investigated by subjecting seed of 90 native species representing 84 genera and 33 families to storage in liquid nitrogen. Seed of 68 native Western Australian species were germinated after storage in liquid nitrogen for two weeks following treatments which involved direct plunging into liquid nitrogen or slow cooling at 0.4°C min^–1 in 15% dimethyl sulphoxide (DMSO) or slow cooling at 0.4°C min^–1 in 35% DMSO. The largest number of species (37) responded positively to direct plunging without pretreatments, with only 10 species responding to slow cooling in 15% DMSO. Thirty one species had enhanced germination and 10 species depressed germination after any of the liquid nitrogen treatments. There were no trends in a species ability to survive liquid nitrogen storage and freezing regime, moisture content, seed size or taxonomic relatedness. However, hard seeded species belonging to the families Caesalpinaceae and Papilionaceae showed a consistently high degree of tolerance to liquid nitrogen storage. Significant physical damage to seed and cotyledons only occurred in Templetonia retusa (Papilionaecae) and this was alleviated by nicking the seed coat. This study indicates that seed of a large proportion of native Western Australian species may be amenable to storage in liquid nitrogen and that at least 40% of the listed rare and endangered species of Western Australia could be maintained in this way.