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Agronomy Journal Abstract -

Leaf Water Potential, Stomatal Resistance, and Temperature Relations in Field-Grown Soybeans1


This article in AJ

  1. Vol. 72 No. 6, p. 986-990
    Received: Dec 17, 1979

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  1. P. K. Jung and
  2. H. D. Scott2



There is a need for daily and seasonal measurements of the field water status of plants in order to characterize their response to soil water deficits. Measurements were made of leaf water potential (Ψ), stomatal diffusive resistance (R), and leaf temperature (T) of irrigated (I) and nonirrigated (N) ‘Forrest’ soybeans [Glycine max (L.) Merr.] grown on Crowley silt loam (a Typic Albaqualf), in a dry season. Values of Ψ in the N soybeans decreased earlier in the day and increased later in the afternoon than Ψ values of I soybeans. The stomates of N plants were partially closed during the daylight hours and closed earlier in the afternoon than stomates of I plants. Leaf temperatures of the N plants increased earlier in the morning and remained higher later in the afternoon than leaf temperatures of I plants. As the drought intensified, differences in Ψ, R, and T between the N and I soybeans increased. Maximum differences during the day were approximately ∆Ψ = −4 bars, ∆R = 6.0 sec/cm, and ∆T = 5.5 C and were usually found at midday and midafternoon late in the season. Generally, the differences in these parameters between moisture regimes were lower at midmorning. The differences in these plant water and temperature parameters were reflected in lower production of total dry matter and seed.

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