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This article in AJ

  1. Vol. 64 No. 4, p. 469-473
     
    Received: Oct 14, 1971


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doi:10.2134/agronj1972.00021962006400040018x

Radial Propagation of Water Potential in Stems1

  1. Fred J. Molz and
  2. Betty Klepper2

Abstract

Abstract

Contraction and expansion of a cotton (Gossypium hirsutum L.) stem in response to a diurnal cycle of leaf water potential is described mathematically using a passive diffusion analysis. The domain of the problem is the stem phloem and associated tissues that are bounded on the outside by impervious bark and on the inside by the xylem that is assigned measured values of leaf water potential. Semiquantitative predictions are derived from numerical solutions of the linear radial diffusion equation, which yield phloem water potential as a function of space and time. Computations relating stem diameter, leaf water potential, and water flow between xylem and phloem fit experimental data. An apparent hysteresis in the stem diameter-leaf water potential relationship is partly explained in terms of the physics of the diffusion process in the stem. This study offers possibilities for relating internal plant water status to measurable external quantities such as stem diameter and for developing a nondestructive technique for the determination of plant xylem water potential.

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