Too high a temperature inhibits germination.
Factors affecting seed dormancy include the presence of certain plant hormones, notably abscisic acid, which inhibits germination, and gibberellin, which ends seed dormancy.
These chemicals, called secondary metabolites, serve plants in many ways, like helping in photosynthesis, inhibiting germination, attracting pollinating insects and deterring pests.
It is best to separate the seed from the fruit tissue before planting, because the pulp inhibits germination until it has been removed by the digestive processes of birds.
The fleshy fruit that surrounds the seed must be removed as this inhibits germination.
In Streptomyces viriochromogenes, low concentrations (200pM) inhibit germination of its own arthrospores, and higher concentrations inhibit porcine Na+/K+ -activated ATPase.
The fruit's pulp contains phenolic compounds which inhibit germination, and thus needs to be removed to promote germination.
Seeds have a hard seed coat, which protects them from harsh arid environments until the next rainfall, but inhibits germination in normal domestic environments.
The shells contain small amounts of a substance that can inhibit germination of seeds, and as they decay they use nitrogen, depriving plants of this valuable nutrient.
Second, apple seeds are coated with a chemical that inhibits germination.