Glassy state and seed storage stability: The WLF kinetics of seed viability loss at T > T(g) and the plasticization effect of water on storage stability

Abstract

The relationship between the glassy state in seeds and storage stability was examined, using the glass transition curve and a seed viability database from previous experiments. Storage data for seeds at various water contents were studied by Williams Landel Ferry (WLF) kinetics, whereas the glass transition curves of seeds with different storage stability were analysed by the Gordon Taylor equation in terms of the plasticization effect of water on seed storage stability. It was found that the critical temperatures (T(g)) for long-term storage of three orthodox seeds were near or below their glass transition temperatures (T(g)), indicating the requirement for the presence of the glassy state for long-term seed storage. The rate of seed viability loss was a function of T-T(g) at T > T(g), which fitted the WLF equation well, suggesting that storage stability was associated with the glass transition, and that the effect of water content on seed storage was correlated with the plasticization effect of water on intracellular glasses. A preliminary examination suggested a possible link between the glass transition curve and seed storage stability. According to the determined WLF constants, intracellular glasses in seeds fell into the second class of amorphous systems as defined by Slade and Levine (Critical Reviews in Food Science and Nutrition 30; 115-360, 1991). These results support the interpretation that the glassy state plays an important role in storage stability and should be a major consideration in optimizing storage conditions.