title: The Cholodny-Went theory does not explain hydrotropism.
abstract: Optimization of water foraging by plants is partially achieved by the ability of roots to direct growth towards high water potential, a phenomenon termed hydrotropism. In contrast to gravitropism and phototropism, which require auxin redistribution, as suggested by the Cholodny-Went theory, hydrotropism is not mediated by the phytohormone auxin, which raises questions about the mechanism underlying this tropic response. Here we specify the open questions in this field of research and discuss the possible interactions of abscisic acid, calcium and reactive oxygen species as part of a dynamic system of sensing water potential in the root tip, transmission of the signal to the root elongation zone and promoting root curvature towards water. We conclude that root hydrotropism is mediated by inter-cellular signals that are not explained by the Cholodny-Went theory.
authors.affiliation: Department of Molecular Biology & Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978 Israel.
authors.forename: Doron
authors.initials: D
authors.lastname: Shkolnik
authors.affiliation: Department of Molecular Biology & Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978 Israel. Electronic address: hillelf@post.tau.ac.il.
authors.forename: Hillel
authors.initials: H
authors.lastname: Fromm
mesh_terms: D000222:Adaptation, Physiological; D055864:Droughts; D006112:Gravitation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D018523:Tropism / Q000235:genetics / Q000502:physiology*; D014867:Water / Q000378:metabolism*
chemical_list: D010937:Plant Growth Regulators; D014867:Water
keywords: Abscisic acid (ABA); Reactive oxygen species (ROS); Tropisms; Water potential