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.
|Original language||English (US)|
|Number of pages||4|
|Journal||Annals of Botany|
|State||Published - Jan 1988|
Bibliographical noteFunding Information:
ACKNOWLEDGEMENTS We thank G. G. Doyle for providing us with seeds of the Ageotropic mutant of Z. mays, and Bill Toland for awarding release-time to Randy Moore for pursuit of this research. This research was supported by grant NAGW-734 from the Space Biology Program of the National Aeronautics and Space Administration (NASA).
- Atomic absorption
- Gravitropism (root)
- Zea mays