Negative gravitropism of stems

This movie shows the negative gravitropic response of a flowering stem of Arabidopsis thaliana after the plant was placed on its side. During the 30 min after the plant was placed on its side it cotinued to droop slightly from the weight of the stem until cells on the bottom side of the shoot began to elongate faster than those on the upper side. The differential growth of the upper and lower cells results in the upward curvature of the stem and after about 3 hours the shoot tip regained a more vertical orientation.