A seed germinates buried in soil, several days before its first leaves appear above the surface. What supplies the growing seedling during those days?

Explanation

A seed is packed with a reserve laid down while it was still attached to the parent plant, and the seedling lives on that reserve until its leaves open and begin making sugar. Drawing food from the soil is impossible because soil contains none to draw, and the young root takes up water and dissolved ions rather than anything the plant could use as fuel.