God gives a seed its body (in other words, its plant) as he has chosen.
The past tense of the verb to choose
points us back to creation, when God ordained that every kind of seed would bring forth plants of its own kind (Genesis 1:11–12). From beginning to end, God is in control of seeds, plants, and human bodies.
38 But God gives it a body as he has chosen, and to each kind of seed its own body.