How do seeds germinate?
Germination is the resumption of growth by a seed embryo under suitable conditions. Water uptake, metabolic activation, and emergence of the embryonic root are key steps. Requirements vary among species, so seeds do not all germinate at the same rate or under identical conditions.
Water, oxygen, and temperature
Water uptake rehydrates tissues and activates enzymes. Stored reserves are converted into compounds usable by the embryo as roots and shoots develop. Oxygen supports respiration, so waterlogging can prevent germination by restricting oxygen supply. Temperature affects metabolism, but temperatures beyond a species' suitable range can impair growth. Some seeds also respond to light, darkness, or particular temperature cycles.
Dormancy and experiment design
Dormancy allows a viable seed to delay germination despite apparently favorable conditions. Seed coats and hormonal regulation can contribute. Some species require cold exposure or natural weakening of the coat. A seed failing to germinate is therefore not necessarily dead. Experiments need comparable seeds, replication, and controlled variables. Germination percentage and subsequent seedling health should be assessed separately.