Summary

You have reached the end of module 4. In this module, you have discovered how important water activity is for genebank processes. You have learned about the different forms water can take inside a seed, and how this influences seed viability. You have discovered different ways genebanks can measure and control the movement of water in and out of seeds, with a view to improving their longevity and viability. In the next section, module 5, you will shift your attention to the process of germination. What makes seeds germinate after they have been stored, and how can genebanks help encourage this?

Module 4 at a glance:

  • Orthodox seeds can tolerate drying.
  • The longevity and viability of orthodox seeds in storage are best when those seeds have been dried to equilibrium in a controlled environment.
  • In dry seeds, water is bound tightly to large molecules: it is therefore less able to facilitate many types of biochemical reactions.
  • In moist seeds, there is water freely circulating within the seed – this water is in a form that can facilitate the biochemical reactions that lead to germination.
  • The conventional method of measuring moisture content of seeds (the gravimetric method) is destructive, expensive, and requires large samples.
  • Measuring the equilibrium relative humidity (eRH) of seeds is a convenient and non-destructive alternative way to measure water activity in seeds.
  • The eRH of seeds can be measured using a water activity meter.

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