Types of dormancy

Seeds in situ face a variety of environmental challenges, and the mechanisms they have evolved in response to these challenges show a lot of diversity. There are three main types of dormancy - all of them maximise the chances of survival for a particular seed in its particular setting:

• Physiological dormancy is a type of dormancy initiated from within the seed.
• Morphological dormancy prevents germination because the embryo is under-developed after the seed has been removed from the mother plant.
• Physical dormancy is a type of dormancy initiated by a hard physical barrier around the fruit or seed, which prevents water from entering the seed.

Some seeds may exhibit more than one of these types of dormancy:

• Combinational dormancy is found in seeds with both physiological and physical dormancy.
• Morphophysiological dormancy is found in species that have both physiological dormancy and immature embryos that need time to grow.

In the next few pages, you will discover more about these types of dormancy, and why successful germination sometimes requires a lot more than just temperature, substrate and water.