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This article in AJ

  1. Vol. 64 No. 4, p. 440-443
    Received: Aug 16, 1971

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Water Potentials in Nonwilted Dianthus Grown in Different Nutrient Solution Concentrations1

  1. Kurt A. Schekel and
  2. Joe J. Hanan2



Experiments were undertaken to determine if Dianthus caryophyllus L. adjusted its internal osmotic potential downward with decreasing solution potential and the concomitant effects on water and turgor potentials. Plants were grown in a gravel substrate, irrigated two to four times daily with solutions of varying potentials, and measurements were made from before sunrise to noon or shortly thereafter on clear days. Plant osmotic potentials adjusted to increase the potential gradient between solution and plant with decreasing solution potential. There were no observable differences between treatments with respect to stomatal aperture or leaf diffusion resistance. The xylem hydrostatic pressure decreased to a greater extent in plants grown in −1.0 bar solutions than hi those grow in −0.3 bar solutions as atmospheric evaporative demand increased. Polynomial regressions of potential on evaporative demand had calculated correlations exceeding 0.90. Differentiation to determine the rate of hydrostatic potential change with change in evaporative demand showed the rate to be highest at low evaporative demands in plants grown in −1.0 bar solutions, gradually decreasing to O at high vapor pressure differences near 16 mm Hg. Carnations in −0.3 bar solutions had rates approaching O at low and high atmospheric demands, with a definite maximum near 9 to 10 mm Hg. The differences between hydrostatic potential and plant osmotic potential, ignoring matric and xylem potentials, showed carnations in −1.0 bar solutions to have consistently lower turgor potentials than plants grown in less concentrated solutions.

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