Change in glass transition temperature upon priming of Impatiens walleriana seeds does not explain their reduced longevity

Abstract

Water is one of the most important factors determining seed storage stability. Rehydration of seeds during osmotic priming modifies seed water sorption properties. In the present study, two glass transitions were detected in impatiens seeds using the calorimetric method. The lower temperature transition was specific to embryos, whereas the higher temperature transition had its origin from seed testa. Osmotic priming in polyethylene glycol (PEG) solution altered seed water sorption characteristics and decreased the glass transition temperature (Tg) of embryos. Primed seeds absorbed less water than control seeds at relative humidity (RH) < 25%, but more water at RH > 25%. The Tg of primed embryos that had been equilibrated at 62% and 67% RH was depressed by about 8°C, when compared to that of control embryos. No differences were observed in Tg during accelerated aging at 42°C and therefore, effect of priming on seed deterioration couldn't be attributed to Tg depression. In conclusion, differences in T g can not explain the differences in longevity for primed versus control seeds.