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This article in AJ

  1. Vol. 76 No. 2, p. 223-228
    Received: Jan 24, 1983

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Physiological Responses to Sorghum Hybrids and Parental Lines to Soil Moisture Stress1

  1. W. C. Hofmann,
  2. M. K. O'Neill and
  3. A. K. Dobrenz2



The development of more drought-resistant sorghum [Sorghum bicolor (L.) Moench.] germplasm depends on a fuller understanding of physiological responses to soil moisture stress. To investigate adaptation to moisture stress, physiological responses of six sorghum hybrids and their respective parental lines were evaluated under two irrigation treatments at Tucson, Ariz., in 1980 and 1981. The soil was a Comoro sandy-loam (coarse-loamy, mixed calcarious, thermic, Typic, Torrifluvent). Apparent photosynthesis, transpiration, diffusive resistance, and temperature differential (ambient temperature minus leaf temperature) were measured under field conditions at weekly intervals. Regression analysis was used to compare the physiological performance of the germplasm over a wide range of environmental conditions. Hybrid 4 was superior to its parental lines for all four physiological characteristics. In 1980, this hybrid was superior to the other hybrids in temperature differential (1.03°C) and transpiration (23.4 μg cm−2 s−1) and had the highest mean apparent photosynthetic rates (45.9 mg dm−2 h−1) and lowest mean diffusive resistance (1.41 cm s−1). Regression analysis is an effective tool that can be used for analyzing the physiological responses across diverse environmental conditions. By regressing the response of individual germplasm against the mean response of the population across all environmental conditions, the slope, mean, and coefficient of correlation were used to evaluate genotype-environment interactions.

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