What seed structure grows out of the testa first?

The seed structure that grows out of the testa first is the radicle, which is the embryonic root of the plant. When a seed germinates, the radicle emerges from the seed coat (testa) and begins to grow downward into the soil, anchoring the plant and absorbing water and nutrients. Following the radicle, the shoot (plumule) will eventually emerge, growing upward towards the light.