What does a seed need before it starts growing?

Germination involves coordinated hydration, metabolism, cell expansion and developmental change in a viable embryo. Oxygen availability can decline in saturated media, and species-specific dormancy can prevent growth even when water and temperature appear suitable. The model deliberately assumes dormancy has been resolved. It is a controlled comparison of requirements, not a universal horticultural prescription. In the model, watch the first root emerge before the shoot and leaves. The progress control represents development stages, not a count of real days.