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Photosynthesis and Stomatal-Conductance Responses of Johnsongrass (Sorghum halepense) to Water Stress

Published online by Cambridge University Press:  12 June 2017

Bryan L. Stuart ,
Daniel R. Krieg  and
John R. Abernathy
Bryan L. Stuart
Affiliation:
Dep. Plant and Soil Sci., Texas Tech. Univ., TX 79401
Daniel R. Krieg
Affiliation:
Dep. Plant and Soil Sci., Texas Tech. Univ., TX 79401
John R. Abernathy
Affiliation:
Weed Science, Texas Agric. Exp. Stn., Lubbock, TX 79401
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Abstract

The influence of water stress on johnsongrass [Sorghum halepense (L.) Pers. ♯ SORHA] physiology was evaluated in a semiarid environment. Stomatal conductance of johnsongrass responded to more negative leaf water potential and increasing leaf temperature. The sensitivity of the leaf temperature effect was dependent on the soil water content. At low soil water content, conductance was limited by low water potential, and increasing leaf temperature had little effect. Conductance of CO2 was related to net photosynthesis in a curvilinear manner, with conductance levels greater than 0.3 mol·m-2· s-1 being in excess of that necessary for maximum photosynthesis. At both high conductance levels and low levels associated with increased water stress, intercellular CO2 concentration increased, indicating nonstomatal limitations to photosynthesis. Decreased osmotic potential provided the highest correlation with the linear decline of photosynthetic rate as stress intensified. The expression of osmotic adjustment in johnsongrass is reported during grain filling. Plants in the milkdough stage of grain filling had approximately 0.3 MPa lower osmotic potential at any relative water content than those at anthesis.

Keywords

Water relationsosmotic adjustmentdesiccation resistanceSORHA
Type
Physiology, Chemistry, and Biochemistry
Information
Weed Science , Volume 33 , Issue 5 , September 1985 , pp. 635 - 639
Copyright
Copyright © 1985 by the Weed Science Society of America 

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References

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