Dielectric study of the hydration mechanism in plant seeds

Part of our recent results concerning the investigation of the hydration mechanism in plant seeds, with a) sorption and desorption studies, b) ac dielectric spectroscopy in the 5 Hz-1 GHz frequency range and c) thermally stimulated currents techniques are described. According to our findings, water in seeds seems to freeze only for concentrations higher than a critical value, whereas for lower hydration it undergoes a glass-like transition, the temperature of which is strongly dependent on the water content of the sample. This glass transition is accompanied by a marked increase of the dc conductivity, the carriers of which are mainly protons, which occurs only after completion of the proton percolation threshold. The biological implications of these findings are discussed.