Samenruhe

Samenruhe, in botanical usage often translated as seed dormancy, is a temporary state in which seeds do not germinate even when environmental conditions are favorable. It is an adaptive trait that allows seeds to persist through periods that are unsuitable for seedling establishment and to spread germination over time, increasing the chances of survival in variable environments. Dormancy can be present at maturity (primary dormancy) and may be re-induced after dispersal by certain environmental cues (secondary dormancy).

Dormancy arises from several underlying mechanisms that are commonly categorized into physiological, physical, and morphophysiological types, with possible combinations. Physiological dormancy involves hormonal balance within the seed, typically high levels of abscisic acid (ABA) and low levels of gibberellins (GA), which suppress embryo growth. Physical dormancy results from a hard or impermeable seed coat that limits water or gas exchange. Morphophysiological dormancy combines an underdeveloped embryo with physiological constraints. Some seeds exhibit coat dormancy, where the outer layers are the primary barrier to germination, while others show a blend of these factors. Environmental factors such as light sensitivity and temperature further modulate dormancy release.

Breaking Samenruhe requires specific cues or treatments. Common methods include stratification, a period of cold (and often moist) storage; warm stratification in some species; scarification, which can be mechanical, thermal, or chemical to weaken the seed coat; after-ripening during dry storage that reduces physiological inhibition; and, in horticulture or research, application of growth regulators such as gibberellins. Understanding dormancy is important for ecology, agriculture, horticulture, and seed conservation, influencing storage, propagation protocols, and restoration practices.