title: Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots.
abstract: The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+.  Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry.  The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots.  In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top.  A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone.  In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone.  Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone.  Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark.  The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.
authors.affiliation: Department of Biology, Kang Reung National University, Kang Woon Do, Korea.
authors.forename: J S
authors.initials: JS
authors.lastname: Lee
authors.forename: M L
authors.initials: ML
authors.lastname: Evans
mesh_terms: D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000378:metabolism*; D002132:Calcium Radioisotopes; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D006540:Herbicides / Q000494:pharmacology; D008027:Light; D010797:Phthalimides / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000378:metabolism*; D014283:Triiodobenzoic Acids / Q000494:pharmacology; D003313:Zea mays / Q000378:metabolism*
chemical_list: D002132:Calcium Radioisotopes; D006540:Herbicides; D010797:Phthalimides; D010937:Plant Growth Regulators; D014283:Triiodobenzoic Acids; C002687:alpha-naphthylphthalamic acid; C052968:2,3,5-triiodobenzoic acid; D002122:Calcium Chloride; D002118:Calcium