Hydraulic resistance of two sorghums varying in drought resistance |
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Authors: | M B Kirkham |
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Institution: | (1) Evapotranspiration Laboratory, Kansas State University, 66506 Manhattan, KS, USA |
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Abstract: | Genotypes of sorghum Sorghum bicolor (L.) Moench] vary in drought resistance. Yet it is not known if their hydraulic resistances vary. The objective of this study
was to determine if the hydraulic resistance of a drought-resistant sorghum was the same as that of a drought-sensitive sorghum.
Leaf water and osmotic potentials were measured daily, during a 14-d period, in leaves of a drought-resistant (‘KS9’) and
a drought-sensitive (‘IA25’) sorghum, which had the roots in pots with a commercial potting soil that was either well watered
or allowed to dry. Soil water potential, adaxial stomatal resistance, and transpiration rate were determined daily. Hydraulic
resistance of the plants was calculated from the slope of the line relating soil water potential minus leaf water potential
versus transpiration rate. When the soil was not watered, the drought-sensitive sorghum had a water potential that averaged
−0.50 MPa lower and an osmotic potential that averaged −0.57 MPa lower, but a similar adaxial stomatal resistance (1.19 s
mm−1), compared with the drought-resistant sorghum. Seven days after the beginning of the experiment, the water potential of the
soil with the drought-sensitive sorghum was −0.25 MPa lower than that of the soil with the drought-resistant sorghum. With
the water-limited conditions, the drought-sensitive sorghum depleted the soil-water reserve more quickly and died 2 d before
the drought-resistant sorghum. Under well watered conditions, the two sorghums had similar water potentials (−1.64 MPa), osmotic
potentials (−2.83 MPa), and adaxial stomatal resistances (0.78 s mm−1). The calculated hydraulic resistance of the two sorghums did not differ and averaged 3.4 × 107 MPa s m−1. The results suggested that the variation in susceptibility to drought between the two genotypes was due to differences in
rate of soil-water extraction.
Contribution No. 86-249-J from the Kansas Agricultural Experiment Station. The paper is dedicated to the memory of Dr Dan
M Rodgers. |
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Keywords: | adaxial stomatal resistance plant osmotic potential plant water potential soil water potential Sorghum bicolor (L ) Moench |
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