科研之友
微信
新浪微博
Facebook
分享链接
摘要
Slow movement of molecules in glassy matrices controls the kinetics of chemical and physical reactions in dry seeds. Variation in physiological activity among seeds suggests that there are differences in mobility among seed glasses. Testing this hypothesis is difficult because few tools are available to measure molecular mobility within dry seeds. Here, motional properties within dry pea cotyledons were assessed using dynamic mechanical analysis. The technique detected several molecular relaxations between -80 and +80 degrees C and gave a more detailed description of water content-temperature effects on molecular motion than previously understood from studies of glass formation in seeds at glass transition (Tg). Diffusive movement is delimited by the alpha relaxation, which appears to be analogous to Tg. beta and gamma relaxations were also detected at temperatures lower than alpha relaxations, clearly demonstrating intramolecular motion within the glassy matrix of the pea cotyledon. Glass transitions, or the mechanical counterpart alpha relaxation, appear to be less relevant to seed aging during dry storage than previously thought. On the other hand, beta relaxation occurs at temperature and moisture conditions typically used for seed storage and has established importance for physical aging of synthetic polymer glasses. Our data show that the nature and extent of molecular motion varies considerably with moisture and temperature, and that the hydrated conditions used for accelerated aging experiments and ultra-dry conditions sometimes recommended for seed storage give greater molecular mobility than more standard seed storage practices. We believe characterization of molecular mobility is critical for evaluating how dry seeds respond to the environment and persist through time.
- 出版日期2011-11
