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This article in AJ

  1. Vol. 65 No. 2, p. 304-306
    Received: Aug 14, 1972

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On the Mechanism of Water-Stress-Induced Stem Deformation1

  1. Fred J. Molz and
  2. Betty Klepper2



Experiments were performed ~o determine where and to what extent stem deformation occurs in the tissue of water-stressed cotton (Gossypium hirsutum L.) plants. Such knowledge is necessary if stem contraction is ever to be used as an index of plant water status. Tension in the xylem of cotton stems was released by severing under water, and portions of stem xylem were subjected to positive hydrostatic pressures in a pressure chamber. The results indicate that the mature xylem of a cotton stem is a rigid material that undergoes negligible elastic deformation in the radial direction when subjected to a hydrostatic stress in the vicinity of 10 to 15 bars. Therefore, any measureable deformation in a water-stressed stem is due almost entirely to dehydration of the living cells found in the phloem and related tissues. These conclusions indicate that it will not be possible to develop a simple relationship between stem diameter changes and plant water status such that a measurement of stem shrinkage can be used to estimate xylem water potential directly. The relationship is complicated by the thickness and water relations of the outer living stem cells.

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