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-orientedroots of Zea mays contain significantly less calcium (Ca) thanblocks that contacted the lower sides of such roots. This gravity-inducedgradient of Ca forms prior to the onset of gravicurvature, anddoes not form across tips of vertically-oriented roots or rootsof agravitropic mutants. These results indicate that (1) Cacan be collected from mucilage of graviresponding roots, (2)gravity induces a downward movement of endogenous Ca in mucilageoverlying the root tip, (3) this gravity-induced gradient ofCa 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 ofCa being a trigger for subsequent redistribution of growth effectors(e.g. auxin) that induce differential growth and gravicurvature. Atomic absorption, calcium, corn, gravitropism (root), Zea mays