Thursday, February 7, 2013

Banking for the future (Part II)

On the subject of seedbanks in my previous blog on 11th December 2012, let’s look further on the types of seeds that exist and how to store them long term. The seed has an embryo and is well protected by the testa or seed coat. When the seed is in storage it is said to be at resting stage or dormant. After a long period or short period of rest the seed can be woken up! This happens in the environment, in the soil. When the conditions are suitable the seed begins to grow. Legume seeds have been found to be alive (viable) for 25 years. Even more remarkable is the fact that wheat seeds buried in the Egyptian tombs for centuries been found to be alive. There are many examples such as these that puzzle us on the seed’s ability to be alive and withstand desiccation and survive the stress. This is one strange mystery of life.

There are a few types of seeds categorised according to the seed’s ability to withstand storage conditions. Seeds that can be stored for very long periods with low moisture content are known as orthodox seeds while those that cannot be stored for long especially in seed banks are known as recalcitrant seeds. Modern methods to store these recalcitrant seeds include tissue culture technology or cryopreservation which is actually storing embryos that have been excised and kept in liquid nitrogen (-1960C).

As mentioned previously seed banks keep seeds safely for a ‘rainy day’. They carry out the basic function of getting new germplasm either through collection or exchange. Each lot of seed is given a passport, so to speak, so that there is no duplication. Conservation is then carried out making available genetic material for crop improvement and to restore it where it has been lost in a country. A gene bank carries out viability tests regularly to ensure stored seeds are always alive and of good quality.

To sum it all we can attribute a seed bank to be an agriculture insurance policy.

By Christina Stephensons

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