Corn root gravitropism

The roots of most plants generally grow in a downward direction to obtain water and mineral nutrients frome the soil. If the orientation of a root is altered, the root will initiate a gravitropic response so that it reorients to the original growth oreintation. The corn seedling shown in this movie was reoriented from vertical to horizontal. About 20 to 30 min after being reorinted (images were taken at 5 min intervals) cells along the upper side of the the root behind the root tip begin to elongate faster than cells along the lower side which causes the root begin curving downward. As more time passes, the root continues to get longer while curving until it is finally reoriented so the tip faces down as it was before the plant was turned on its side.