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℃ for different periods of time. The results showed that the optimum MC for seed and embryo storage varied between species （0.057 g H20/g DW for maize embryos, 0.045 g H20/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 （△Azz） in elms, maize and safflower embryos was compatible with the optimum moisture content.
Ming Zhang Jia-Jin Zhuo Xu Wang Sen Wu Xiao-Feng Wang
The aim of the present work was to investigate the effects of osmoconditioning on chilling injury in chilling-sensitive soybean （Glycine max （L.） Merr. Zhonghuang No. 22） seeds during imbibition. Low temperatures reduced the germination rate and no seed germinated at 1 ℃. Osmoconditioning of seeds at 20℃ with a polyethylene glycol-8000 （PEG8000） solution at 1.5 MPa for 72 h followed by drying back to their initial moisture content （MC） reduced their chilling sensitivity. The phenylarsine oxide （PAO）, an inhibitor of protein tyrosinephosphatases, was used to investigate the possible involvement of phosphorylation-dephosphorylation of Tyr residues in the plasma membrane composition and function when seeds were osmoconditioned. The results showed the germination of osmoconditioned seeds decreased significantly when PAO was added in PEG solution after chilling treatment. PAO inhibited changes in composition of plasma membrane phospholipids and fatty acid induced by osmocondition, indicated that tyrosine protein phosphorylation is involved in the regulatory mechanisms of osmocondition-responsive chilling in soybean seeds. Western blot result further indicated that osmocondition treatment improved the activity of plasma membrane H^＋-ATPase after chilling treatment, but this effect was abolished by PAO. The possible regulation mechanism by Tyr protein phosphorylation is discussed.
