If we have sown [the good seed of] spiritual things in you, is it too much if we reap material things from you?

You fool! Every time you plant seed you sow something that does not come to life [germinating, springing up and growing] unless it first dies.

The seed you sow is not the body (the plant) which it is going to become, but it is a bare seed, perhaps of wheat or some other grain.