Seed ageing of four Western Australian species in relation to storage environment and seed antioxidant activity

The influence of the storage environment on seed viability and antioxidant potential was examined for four species native to Western Australia: Acacia bivenosa DC., Anigozanthos manglesii D. Don, Banksia ashbyi E.G. Baker, and Mesomelaena tetragona (R. Br.) Benth. Seeds were stored at four water contents (at c. 5%, 11-15%, 20-23% and 50% relative humidity) at each of five temperatures (-196, -18, 5, 23 and 50degreesC), and seed germination and seedling vigour monitored over an 18-month period. Deterioration was apparent in all species (except A. bivenosa) stored at 50degreesC, with 11% RH maximizing longevity for B. ashbyi and M. tetragona seeds, and 5% or 11% RH preventing deterioration for A. manglesii seeds. Seed viability generally remained high for all species stored at 23degreesC or less. Notably, however, germination and seedling vigour of A. manglesii and M. tetragona seeds gradually declined when stored at -18degreesC, suggesting that storage at this temperature was detrimental. The antioxidant activity of lipid extracts of seeds after 18 months storage at 5, 23 and 50degreesC was also examined to determine whether the seed viability decline was associated with a loss of antioxidants. Antioxidant activity varied between storage treatments and was not related to seed viability.