title: How roots perceive and respond to gravity.
abstract: Graviperception by plant roots is believed to occur via the sedimentation of amyloplasts in columella cells of the root cap.  This physical stimulus results in an accumulation of calcium on the lower side of the cap, which in turn induces gravicurvature.  In this paper we present a model for root gravitropism integrating gravity-induced changes in electrical potential, cytochemical localization of calcium in cells of gravistimulated roots, and the interdependence of calcium and auxin movement.  Key features of the model are that 1) gravity-induced redistribution of calcium is an early event in the transduction mechanism, and 2) apoplastic movement of calcium through the root-cap mucilage may be an important component of the pathway for calcium movement.
authors.affiliation: Department of Biology, Baylor University, Waco, Texas 76798, USA.
authors.forename: R
authors.initials: R
authors.lastname: Moore
authors.forename: M L
authors.initials: ML
authors.lastname: Evans
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D018522:Gravitropism / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism / Q000502:physiology; D018521:Plant Physiological Phenomena; D018518:Plant Root Cap / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure*; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D018087:Plastids / Q000502:physiology*; D003313:Zea mays / Q000648:ultrastructure
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; C030737:indoleacetic acid; D000040:Abscisic Acid; D002118:Calcium