Rapid Communications

Planta

, Volume 197, Issue 2, pp 410-413

Hydrotropism in roots: sensing of a gradient in water potential by the root cap

  • Mamoru TakanoAffiliated withInstitute of Genetic Ecology, Tohoku University
  • , Hideyuki TakahashiAffiliated withInstitute of Genetic Ecology, Tohoku University Email author 
  • , Tadashi HirasawaAffiliated withFaculty of Agriculture, Tokyo University of Agriculture and Technology
  • , Hiroshi SugeAffiliated withInstitute of Genetic Ecology, Tohoku University

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Abstract

Roots of the agravitropic pea (Pisum sativum L.) mutant, ageotropum, responded to a gradient in water potential as small as 0.5 MPa by growing toward the higher water potential. This positive response occurred when a sorbitol-containing agar block was unilaterally applied to the root cap but not when applied to the elongation region. Unilateral application of higher concentrations of sorbitol to the elongation region caused root curvature toward the sorbitol source, presumably because of growth reduction on the water-stressed side. The control blocks of plain agar applied to either the root cap or the elongation region did not cause significant curvature of the roots. These results demonstrate that hydrotropism in roots occurs following perception of a gradient in water potential by the root cap.

Key words

Hydrotropism Mutant (pea) Pisum (ageotropum mutant) Root cap Water potential