There are two types of germination.
In epigeal germination,the cotyledons rise above the ground such as mung bean and sunflower.
In hypogal germination,the cotyledons remain below the ground such as broad bean and maize.
When the testa rupture,the radicle grows downwards into the soil. The young root develops root hairs to absorb water and minerals from the soil. The plumule grows upwards and develops the first foliage leaves. The cotyledons shrink as their food reserve is used up and leaves take over the role of food production.