Corn grows from the root up. Like all plants, corn gets its energy from the Sun and its water and nutrients from the ground through its roots. With its energy and food, it grows the stalks and leaves that make the plant - the leaves keep reaching upward from the ground. Clipping the tops of these leaves won’t hurt the corn. As long as they have their roots and can get food and energy from the Sun, the leaves will keep growing, like other plants related to grass.