17 Facts About Seed dormancy

Seed dormancy is an evolutionary adaptation that prevents seeds from germinating during unsuitable ecological conditions that would typically lead to a low probability of seedling survival.

An important function of seed dormancy is delayed germination, which allows dispersal and prevents simultaneous germination of all seeds.

Exogenous Seed dormancy is caused by conditions outside the embryo and is often broken down into three subgroups:.

Physical dormancy is the result of impermeable layer that develops during maturation and drying of the seed or fruit.

Physical Seed dormancy is believed to have developed more than 100 million years ago.

Therefore, the timing of the mechanisms that breaks physical Seed dormancy is critical and must be tuned to environmental cues.

Physical dormancy has been identified in the seeds of plants across 16 angiosperm families including:.

Physical Seed dormancy has been recorded in a few species of Cycadales with thick sclerotesta and slow embryo development, for example Cycas revoluta and Zamia floridana, but not in any of the other groups of extant gymnosperms.

Generally, physical dormancy is the result of one or more palisade layers in the fruit or seed coat.

Physiological dormancy prevents embryo growth and seed germination until chemical changes occur.

Physiological Seed dormancy is indicated when an increase in germination rate occurs after an application of gibberellic acid or after Dry after-ripening or dry storage.

In some seeds physiological dormancy is indicated when scarification increases germination.

Physiological dormancy is broken when inhibiting chemicals are broken down or are no longer produced by the seed; often by a period of cool moist conditions, normally below 39F, or in the case of many species in Ranunculaceae and a few others, 24F.

Some plants like Peony species have multiple types of physiological Seed dormancy, one affects radicle growth while the other affects plumule growth.

Combinational dormancy occurs in some seeds, where dormancy is caused by both exogenous andendogenous conditions.

Secondary dormancy occurs in some non-dormant and post dormant seeds that are exposed to conditions that are not favorable for germination, like high temperatures.

The mechanisms of secondary Seed dormancy are not yet fully understood but might involve the loss of sensitivity in receptors in the plasma membrane.