Manipulating longevity during storage
Commercial seed producers have known for some time that deliberately altering the moisture content of seeds can affect their viability. A number of methods can be used to achieve this, ranging from soaking seeds in pure water to applying chemical agents in order to adjust moisture content. For instance, seeds that are rehydrated then dried again just prior to germination can show more rapid, uniform germination – this process is called ‘priming’.
Until recently, this knowledge has had limited uptake in genebanks. There were fears that the lifespan of primed seeds in long-term storage may be reduced. However, new evidence shows that this process could, in fact, be very useful in genebanks.
Case study: Primed and ready
In a study of a temperate woodland plant, common foxglove (Digitalis purpurea), scientists from the Royal Botanic Gardens at Kew in the United Kingdom kept seeds in experimental storage for 14 or 28 days. The seeds were then primed - taken out of storage and rehydrated enough to wake up biochemical pathways within the seed, without actually starting germination, then dehydrated again and placed back into storage. As a result, the seeds showed substantially increased life spans.
The effect of priming is to rejuvenate the seeds. This intriguing result was greatest in the species with shortest-lived seeds. The scientists found that repeated cycles of storage and priming yielded further benefits to longevity. This kind of dehydration-rehydration treatment could be of great interest to genebanks. There are hopes that, used alongside regeneration, processes like this could improve the survival of seeds in storage.
Pause for reflection
Many experiments that have contributed to our knowledge about seed longevity have been carried out under experimental storage conditions (conditions of high temperature and humidity which deliberately speed up aging reactions). Give yourself a few minutes to think about this. How can we be sure that the biological processes are similar, whether germination takes place under experimental storage conditions or actual genebank storage conditions?
Differences between species