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This article in AJ

  1. Vol. 71 No. 2, p. 321-325
    Received: Apr 29, 1978

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Leaf Conductance and Leaf-Water Potential Relationships for Two Soybean Cultivars Grown Under Controlled Irrigation1

  1. R. E. Carlson,
  2. N. N. Momen,
  3. O. Arjmand and
  4. R. H. Shaw2



Both leaf-water potential and leaf conductance are used singly or in combination as important indicators of soil moisture stress. The relationship between these two parameters may not be unique between species or even within a species, depending upon environmental conditions.

These relationships were studied in soybeans [Glycine max (L.) Merr.] by growing plants in large potometers in the field under controlled soil moisture conditions. The potometers were previously filled with the top 15 cm of a Nicollet silt loam (Aquic Hapludolls, fine-loamy mixed mesic). The plants were subjected to four independent drydown stress periods during critical reproductive stages of growth. Soil moisture was controlled by hand watering and the use of an automatic shelter, which covered the plots during periods of rainfall. Five levels of soil moisture were imposed during each of the four stress periods. Soil moisture was monitored with a neutron soil moisture probe, and leaf-water potential was measured by using a pressure bomb. Leaf conductance data were collected using a diffusion porometer.

Leaf conductance was significantly correlated with leafwater potential over most days; however, a unique nonlinear relationship between these two parameters was not established. Atmospheric demand, time of day, and some type of moisture stress hardening contributed as significant sources of variation. Although not consistent over all days, these two cultivars were shown to differ significantly in their leaf-water potential, leaf-conductance relationships.

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