Seed Dormancy Classifications

Seed Dormancy Classifications vary greatly. Many seed dormancy classification schemes have been proposed over the years. Any classification scheme for seed dormancy must have a practical use. This is especially true if you happen to be a seed analyst. It should be simple as well as useable.

Plant and seed physiologists have put forth hundreds of dormancy classification schemes and this has made understanding seed dormancy hard to understand and confusing at best. Many of the schemes are strictly for bud dormancy in plants and not relevant to seeds.

Here's a nice scheme that I've found that works well when dealing with seed dormancy and trying to figure out why seeds aren't germinating:

Innate Seed Dormancy

Innate dormancy is present within the seed when it reaches physiological maturity It is imposed upon the seed by the mother plant and remains for some time after the seed is shed.

Often, the seed need only go through an after-ripening period for it to disappear. But, it may also be combined in the seed with other types of dormancy so that the seed remains dormant after the innate dormancy mechanism is removed.

Enforced Seed Dormancy

Enforced dormancy is literally "forced" upon the seed by some limitation of the germination environment. Seeds requiring light, alternating temperaturess, or light/dark conditions fall into this category. One or more of these conditions need to be satisfied for the seed to begin germination.

This type of dormancy disappears once the missing condition(s) are supplied. The environment supplies the strict requirements that the seed needs to soften membranes, cause physiological shifts in inhibitors and promotor chemicals, cause different metabolic pathways to activate, or a combination of these and the seed begins to germinate and grow.

Certain seed species are more sensitive to environmental conditions and controls. You'll find that freshly harvested seed is more sensitive to the environmental parameters that cause this type of dormancy. As the seed ages, the narrow environmental conditions that must be met to break this dormancy widen and the seed becomes less sensitive to them.

Induced Seed Dormancy

Induced dormancy has also been referred to as secondary dormancy. In this case, the dormancy is induced upon the seed after conditions of innate and enforced dormancy have been broken or lost from the seed.

Induced dormancy occurs when the seed has imbibed water but has been placed under extremely unfavorble conditions for germination. When later placed under more favorable conditions the seed fails to germinate while still remaining viable. It is often very hard to entice seeds displaying induced dormancy to germinate.

Even seed species that don't normally display dormancy may fall into a state of induced dormancy under the right conditions.

If you wish to go back to the previous page, go to: Dormancy Mechanisms.