Water sorption characteristics of seeds of four Western Australian species

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The relationship between storage temperature, relative humidity and seed water content was investigated 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. Water sorption isotherms were constructed at 5, 23 and 50°C and the enthalpy of water sorption was calculated by van't Hoff analysis. Seeds of three species, A. manglesii, B. ashbyi and M. tetragona, showed a sigmoidal relationship between seed water content and relative humidity. Intact seeds of Acacia bivenosa maintained a constant water content at temperatures of 23°C or less due to the impermeable seed coat; however, isotherms of scarified seeds were similar in shape to those of the other species at all temperatures. The enthalpy of water sorption ranged from -19 kJ mol-1 for M. tetragona seeds to -29 kJ mol-1 for B. ashbyi seeds and was dependent on water content. However, all species had a maximum sorption strength at 2-6% water content and three regions of water-binding strength were evident. Each of these species has water sorption characteristics consistent with orthodox storage behaviour and the results of this study provide a framework for improving seed storage methods for the highly diverse Western Australian flora.

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Australian Journal of Botany