A gradient of endogenous calcium forms in mucilage of graviresponding roots of Zea mays.
Agar blocks that contacted the upper sides of tips of horizontally-oriented roots of Zea mays contain significantly less calcium (Ca) than blocks that contacted the lower sides of such roots.  This gravity-induced gradient of Ca forms prior to the onset of gravicurvature, and does not form across tips of vertically-oriented roots or roots of agravitropic mutants.  These results indicate that (1) Ca can be collected from mucilage of graviresponding roots, (2) gravity induces a downward movement of endogenous Ca in mucilage overlying the root tip, (3) this gravity-induced gradient of Ca does not form across tips of agravitropic roots, and (4) formation of a Ca gradient is not a consequence of gravicurvature.  These results are consistent with gravity-induced movement of Ca being a trigger for subsequent redistribution of growth effectors (e.g. auxin) that induce differential growth and gravicurvature.
Moore
R
R
Department of Biology, Baylor University, Waco, Texas 76798, USA.
Fondren
W M
WM
D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D009154:Mutation; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D003313:Zea mays / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D002118:Calcium