Germination is the development of a young embryo into a young seedling. We need germination for plants to grow. With no plants there would be less oxygen and less food for animals. In germination you need water, the right temperature, sunlight, minerals, and oxygen.
You need water to begin germination. When water soaks the seed coat, it splits open. The seed coat is the outer layer of the seed coat that protects it. Water softens the seed coat, making it easier to split.
The temperature depends on the seed. Some seeds need to be hot before they can grow. These seeds are probably in areas with a lot of heat or fire. When fires kill the mature plants, the seeds can germinate. Now that the mature plants are dead, the seedlings have room to germinate. If the seeds could grow any time, there would not be many seeds left.
This is why seeds need minerals and energy. The part of the seed that turns into a seedling is called the embryo. The embryo in the seed needs energy to germinate. As the embryo develops it will use up all its stored food. After it has used up all its stored food, it will die unless it gets energy to make its own food. The process of making its own food is called photosynthesis. The seeds also need nutrients and minerals to grow.
The seeds need oxygen to begin respiration. Respiration is breathing in oxygen and breathing out carbon dioxide. For plants, it is the opposite. Respiration lets germinating seeds make energy for photosynthesis.
Even you give a plant everything it needs; you cannot force it to grow. It takes time for the seeds to grow. Just like we cannot become grown-ups in a few days just because we eat right foods and get exercise, plants are the same. Plants can take weeks or even 50 years to grow. How long it takes to grow usually depends on the toughness of the seed coat. If the seed coat is thick, it will take a long time to grow, because it will take a long time for the seed coat to soften. If the seed coat is thin, it will take less time to grow.
The seeds of some tropical plants take days to germinate if you give the seeds everything it needs. Other seeds go through dormancy. Dormancy is when seeds are inactive, like as if they were asleep. Dormant seeds do not germinate for weeks or months. Dormancy stops seeds from sprouting, before their environment is ready for germination. An example of when dormancy might occur is if there was no rain or sunshine.
After water splits open the seed coat, the main root begins to grow into the soil. The main root begins to grow. The roots that spread from the main root, anchor down the seedling down. They also take in water and minerals from the soil, so the embryos can get what they need to grow. After a while, leaves begin to grow. The leaves and roots continue to keep growing.