These movements are spoken of as different kinds of geotropic curvatures.
Such small granules have been observed in the sensitive cells, and there is an evident correlation between these and the power of receiving the geotropic stimulus.
Response to the action of gravity appears to be associated with the movements of starch grains in certain cellsstatolith cellsby which pressure is exerted on the cytoplasm and a stimulus set up which results in the geotropic response.
As soon as the confluent petioles protrude from the seed they bend down, as they are strongly geotropic, and penetrate the ground.