<Li> Light or darkness can be an environmental trigger for germination and is a type of physiological dormancy . Most seeds are not affected by light or darkness, but many seeds, including species found in forest settings, will not germinate until an opening in the canopy allows sufficient light for growth of the seedling . </Li> <P> Scarification mimics natural processes that weaken the seed coat before germination . In nature, some seeds require particular conditions to germinate, such as the heat of a fire (e.g., many Australian native plants), or soaking in a body of water for a long period of time . Others need to be passed through an animal's digestive tract to weaken the seed coat enough to allow the seedling to emerge . </P> <P> Some live seeds are dormant and need more time, and / or need to be subjected to specific environmental conditions before they will germinate . Seed dormancy can originate in different parts of the seed, for example, within the embryo; in other cases the seed coat is involved . Dormancy breaking often involves changes in membranes, initiated by dormancy - breaking signals . This generally occurs only within hydrated seeds . Factors affecting seed dormancy include the presence of certain plant hormones, notably abscisic acid, which inhibits germination, and gibberellin, which ends seed dormancy . In brewing, barley seeds are treated with gibberellin to ensure uniform seed germination for the production of barley malt . </P> <P> In some definitions, the appearance of the radicle marks the end of germination and the beginning of "establishment", a period that utilizes the food reserves stored in the seed . Germination and establishment as an independent organism are critical phases in the life of a plant when they are the most vulnerable to injury, disease, and water stress . The germination index can be used as an indicator of phytotoxicity in soils . The mortality between dispersal of seeds and completion of establishment can be so high that many species have adapted to produce large numbers of seeds . </P>

Dormant seeds are stimulated to sprout by the effect of