<P> Amyloplasts are plastids, specifically leucoplasts . Plastids are a specialized class of cellular organelles that carry their own genome and are believed to be descendants of cyanobacteria (blue - green algae) which formed a symbiotic relationship with the eukaryotic cell . </P> <P> Starch synthesis and storage also takes place in chloroplasts, a type of pigmented plastid involved in photosynthesis . Amyloplasts and chloroplasts are closely related, and amyloplasts can turn into chloroplasts; this is for instance observed when potato tubers are exposed to light and turn green . </P> <P> In the root cap (a tissue at the tip of the root) there is a special subset of cells, called statocytes . Inside the statocyte cells, some specialized amyloplasts are involved in the perception of gravity by the plant (gravitropism). These specialized amyloplasts--called statoliths--are denser than the cytoplasm and can sediment according to the gravity vector . The statoliths are enmeshed in a web of actin and it is thought that their sedimentation transmits the gravitropic signal by activating mechanosensitive channels . The gravitropic signal then leads to the reorientation of auxin efflux carriers and subsequent redistribution of auxin streams in the root cap and root as a whole . The changed relations in concentration of auxin leads to differential growth of the root tissues . Taken together, the root is then turning to follow the gravity stimuli . Statoliths are also found in the endodermic layer of the inflorescence stem . The redistribution of auxin causes the shoot to turn in a direction opposite that of the gravity stimuli . </P>

In the image of a plant cell below click on the leukoplast (leucoplast)