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.
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This work was supported by grants from the Institute of Space and Astronautical Science (Sagamihara, Japan) and by Grants-in-Aid from the Ministry of Education, Science and Culture of Japan to H. T. and H. S. We thank Dr. Tom K. Scott, University of North Carolina at Chapel Hill, and Dr. Hironao Kataoka, Tohoku University, for their critical reading of our manuscript.
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Takano, M., Takahashi, H., Hirasawa, T. et al. Hydrotropism in roots: sensing of a gradient in water potential by the root cap. Planta 197, 410–413 (1995). https://doi.org/10.1007/BF00202664
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DOI: https://doi.org/10.1007/BF00202664