GRAVITROPISM -MECHANISM

=Gravitropism in Roots= [image:http://i.imgur.com/V0prbhX.jpg?1] Root cap cells contain small starch granules called amyloplasts (or statoliths) which are packaged into little bundles. These bundles are relatively heavy and will sink to the bottom. Removing these starch granules renders the roots incapable of responding to the direction of gravity. Thus it is believed that these granules act as a gravity sensor, stimulating the transport of auxin to the lower side of the root. In roots the Auxin inhibits cell growth and thus the cells elongate and grow faster on the opposing side of the root. This causes the root to curve downward with the direction of gravity. This is known as a '''positive gravitropism'''. [image:http://i.imgur.com/tDI90r4.gif]