Optimizing seed water content: relevance to storage stability and molecular mobility

This research was conducted to determine the optimum moisture content (MC) that gave maximum longevity to seeds. Three species were used to represent seeds with different dry matter reserves, which gives them different sorption properties: maize (Zea mays L.), elm (Ulmus pumila L.) and safflower (Carthamus tinctorius L.). The seeds of elm, safflower, and maize embryos with MC ranging from 0.00-0.15 g H2O/g dry weight (DW) were stored at 35 degrees C for different periods of time. The results showed that the optimum MC for seed and embryo storage varied between species (0.057 g H2O/g DW for maize embryos, 0.045 g H2O/g DW for elm, and 0.02 g H2O/g DW for safflower). Drying below this optimum MC increased the aging rate and there were detrimental effects of drying. The relative humidity corresponding to optimum MC in embryos of maize, elms and safflower was about 15%, 12% and 7% respectively, according to the lipid composition of the embryos. The data provided confirmatory evidence that molecular mobility (DeltaAzz) in elms, maize and safflower embryos was compatible with the optimum moisture content.