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This article in AJ

  1. Vol. 60 No. 4, p. 408-413
     
    Received: Dec 30, 1967


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doi:10.2134/agronj1968.00021962006000040023x

Water Potential Measurements of an Intact Plant-Soil System1

  1. Glenn J. Hoffman and
  2. William E. Splinter2

Abstract

Abstract

Thermocouple psychrometers were used to measure the water potential of an intact plant-soil system. The system consisted of a young tobacco plant grown in a container of fine sandy loam soil. The effects of soil water potential, diurnal fluctuations, and atmospheric relative humidity on the leaf water potential within a leaf and at different locations on the plant were studied.

Water potential was found to decrease from the base of the leaf to the tip. Leaves at the base of the plant were found to have lower water potentials than leavesnear the middle. The soil water potential decreased linearly with time as evapotranspiration occurred in the system. The site of measurement on the leaf, atmospheric relative humidity, and diurnal variations were found to affect the relationship between leaf and soil water potential. At a constant relative humidity a linear relationship was obtained when the leaf water potential was measured at the base of the bottom leaves or at a given time each day to eliminate diurnal variations. In general, however, the relationship between leaf and soil water potential was not found to be linear. Soil water potential, atmospheric relative humidity, and diurnal variations were found to reduce the leaf water potential by at least 100% in tobacco if altered within the range found under field conditions.

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