starch-statolith hypothesis

A possible explanation for the way plants perceive gravity. Most gravity-sensitive organs contain specialized cells called statoliths, in their cytoplasm. The statoliths gradually fall to the lower side of the cell under the influence of gravity. The settling out of these grains in reoriented cells is said to provide an internal stimulus, which is transmitted to the growing region of the organ so that appropriate amendments to the growth pattern can be made. These growth movements restore the original position of the cells and hence of the whole plant part. See also geotropism.