Intensity of hydrostimulation for the induction of root hydrotropism and its sensing by the root cap |
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Authors: | H TAKAHASHI T K SCOTT |
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Institution: | Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai 980, Japan;Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA |
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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. |
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Keywords: | Pisum sativum L Zea mays L pea corn ageotropum gravitropism hydrotropism hydrostimulation hydrosensing root cap |
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