Infection of the coleoptile occurs as it emerges from the embryo. The middle portion of the coleoptile is the area where the shoot curvature occurs. When the growth-promoting chemical was distributed evenly the coleoptile grew straight. The coleoptile is then pushed up through the ground until it reaches the surface. In some cases (coleoptile growth), auxin-promoted cellular expansion occurs in the absence of cell division. Coleoptile is the pointed protective sheath covering the emerging shoot in monocotyledons such as grasses.