title: Intensity of hydrostimulation for the induction of root hydrotropism and its sensing by the root cap.
abstract: Roots of Pisum sativum L. and Zea mays L. were exposed to different moisture gradients established by placing both wet cheesecloth (hydrostimulant) and saturated aqueous solutions of various salts in a closed chamber.  Atmospheric conditions with different relative humidity (RH) in a range between 98 and 86% RH were obtained at root level, 2 to 3mm from the water-saturated hydrostimulant.  Roots of Silver Queen corn placed vertically with the tips down curved sideways toward the hydrostimulant in response to approximately 94% RH but did not respond positively to RH higher than approximately 95%.  The positive hydrotropic response increased linearly as RH was lowered from 95 to 90%.  A maximum response was observed at RH between 90 and 86%.  However, RH required for the induction of hydrotropism as well as the responsiveness differed among plant species used; gravitropically sensitive roots appeared to require a somewhat greater moisture gradient for the induction of hydrotropism.  Decapped roots of corn failed to curve hydrotropically, suggesting the root cap as a major site of hydrosensing.
authors.affiliation: Institute of Genetic Ecology, Tohoku University, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: T K
authors.initials: TK
authors.lastname: Scott
mesh_terms: D002122:Calcium Chloride; D002254:Carbonates; D006813:Humidity; D018532:Pisum sativum / Q000254:growth & development; D018518:Plant Root Cap / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development*; D011188:Potassium; D011189:Potassium Chloride; D012965:Sodium Chloride; D018523:Tropism / Q000502:physiology*; D014867:Water; D003313:Zea mays / Q000254:growth & development
chemical_list: D002254:Carbonates; D014867:Water; D012965:Sodium Chloride; D011189:Potassium Chloride; C037593:potassium carbonate; D002122:Calcium Chloride; D011188:Potassium