- Statolith
Statoliths are a specialized form of
amyloplast s involved ingravity perception byplant s.These specialized amyloplasts are denser than the
cytoplasm and can sediment according to thegravity vector. They are found in a special subset of cells of theroot cap (a tissue at the tip of theroot ) calledstatocyte s. Statoliths are enmeshed in a web ofactin and it is thought that their sedimentation transmits the gravitropic signal by activatingmechanosensing channels. The gravitropic signal then leads to reorientation ofauxin efflux carrier s and subsequent redistribution ofauxin streams in root cap and root as a whole. The changed relations in concentration of auxin leads todiffererential growth of the root tissues. Taken together, the root is then turning, following the gravity stimuli.Statocyts 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. As these are a subclass of amyloplasts, they originally come from leucoplasts [missing reference !, this statement is in inconsistency with shown figure and with Buchanan et al (eds) Biochemistry and Molecular Biology of Plants; Rockville, Maryland] . All of these different 'plasts' come from proplastids.Compare
*
Plastid
**Chloroplast andetioplast
**Chromoplast
**Leucoplast
***Amyloplast
****Statolith
***Elaioplast
***Proteinoplast
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