SEED DORMANCY

How long can a seed be asleep?

Seeds not only like travelling but also like sleeping. A large number of seeds are unable to germinate immediately after they fall from the parent plant, so they remain "asleep" for a certain time. This state in which seeds fail to germinate despite the availability of favourable germination conditions, such as warmth and moisture, is called dormancy. It works as a mechanism which allows the plant to germinate only when the conditions are fully favourable for survival of the seedlings. The period of dormancy can last from a few weeks up to many years.

Plants used in agriculture are usually non-dormant. All they need is some moisture to get their biochemistry activated, and a temperature warm enough for it to proceed. Seeds taken from the wild, however, frequently exhibit dormancy.

There are three main types of seed dormancy:

  • Physical dormancy due to seed or fruit coat being resistant, particularly to water uptake. This form of dormancy may be broken in the laboratory by scarification or chipping of the seed coat. There may be germination inhibitors in the seed coat and in this case, removal of the coat may be important.
  • Physiological dormancy is caused by biochemical germination inhibitors. Various treatments break this dormancy. An interesting one is the use of smoke.
  • Morphological dormancy occurs in seeds with immature embryos. These can only be germinated after allowing sufficient time under appropriate conditions for the embryo to mature.

This apparently simple survival strategy of seeds can be a deep and complex process which combines several of the basic dormancy types, and may need the application of several factors in a laboratory to get seeds to germinate.

© ENSCONET. European Native Seed Conservation Network