The gravity sensing in gravitropism is by due to the presence of the organ statocysts. Statocytes are the cells containing the sedimenting starch grains. There is more than one statoliths in the statocyte. Statoliths are the amyloplast which is formed of group of starch grains contained inside a cell membrane. The horizontal position of the root which will cause the displacement of the statoliths in response to the gravity. This results in the change in the potential of the cell membrane. This in turn results in the stimulation and flow of the calcium and auxin towards lower side of the root. The difference in the activity of the auxins between the upper and lower side of the root result in the growth of the root downwards.
