Abstract:

【Objective】 The seeds of elm (Ulmus pumila L.), maize (Zea mays L.) and safflower (Carthamus tinctorius L.) with different characteristics of desiccation-tolerance and chemical component were chosen to study the relationship between moist content for seed storage and the molecular mobility as well as the soluble sugar. 【Method】 The EPR spectra of the spin labeled axes of seeds with different moist contents were examined with CP (3-carboxy-proxyl) as a spin probe and using 2Azz as a measure of molecular mobility. DSC and HPLC were used to measure glass transition temperature and the content and composition of sugar.【Result】 The changes of molecular mobility in ultradried seeds with different moisture contents were opposite to the changes of storage stability, which supposed that molecular mobility could be used as a simple method to predict the optimum moisture content of ultradried storage. The safflower seed own higher value of Tg than elm and maize seeds, there was a higher content of raffinose in safflower than the content in elms or maize. 【Conclusion】 Molecular mobility was compatible with the optimum moisture content, and the temperature of glass transition (Tg) could not be used solely to predict precise conditions of optimum storage. The optimum moisture content of ultradried storage may be related to the matter accumulated during the mature dehydration.

Key words: ultradried seed storage, molecular mobility, glass state, soluble sugar